Enable CA1821, CA1825-CA1834 (#33041)

* Enable CA1821, CA1825-CA1834 Contributes to https://github.com/dotnet/aspnetcore/issues/24055
2021-05-26 16:05:12 -07:00 · 2021-05-26 16:05:12 -07:00 · e4f7bfb435
--- a/.editorconfig
+++ b/.editorconfig
@ -91,9 +91,40 @@ dotnet_diagnostic.CA1802.severity = warning
 # CA1805: Do not initialize unnecessarily
 dotnet_diagnostic.CA1805.severity = warning

+# CA1823: Remove empty Finalizers
+dotnet_diagnostic.CA1821.severity = warning
+
 # CA1823: Avoid unused private fields
 dotnet_diagnostic.CA1823.severity = warning

+# CA1823: Avoid zero-length array allocations
+dotnet_diagnostic.CA1825.severity = warning
+
+# CA1826: Do not use Enumerable methods on indexable collections. Instead use the collection directly
+dotnet_diagnostic.CA1826.severity = warning
+
+# CA1827: Do not use Count() or LongCount() when Any() can be used
+dotnet_diagnostic.CA1827.severity = warning
+
+# CA1828: Do not use CountAsync() or LongCountAsync() when AnyAsync() can be used
+dotnet_diagnostic.CA1828.severity = warning
+
+# CA1829: Use Length/Count property instead of Count() when available
+dotnet_diagnostic.CA1829.severity = warning
+
+# CA1830: Prefer strongly-typed Append and Insert method overloads on StringBuilder
+dotnet_diagnostic.CA1830.severity = warning
+
+# CA1831: Use AsSpan or AsMemory instead of Range-based indexers when appropriate
+# CA1832: Use AsSpan or AsMemory instead of Range-based indexers when appropriate
+# CA1833: Use AsSpan or AsMemory instead of Range-based indexers when appropriate
+dotnet_diagnostic.CA1831.severity = warning
+dotnet_diagnostic.CA1832.severity = warning
+dotnet_diagnostic.CA1833.severity = warning
+
+# CA1834: Consider using 'StringBuilder.Append(char)' when applicable
+dotnet_diagnostic.CA1834.severity = warning
+
 # CA2012: Use ValueTask correctly
 dotnet_diagnostic.CA2012.severity = warning

@ -110,5 +141,15 @@ dotnet_diagnostic.CA1507.severity = suggestion
 dotnet_diagnostic.CA1802.severity = suggestion
 # CA1805: Do not initialize unnecessarily
 dotnet_diagnostic.CA1805.severity = suggestion
+# CA1823: Avoid zero-length array allocations
+dotnet_diagnostic.CA1825.severity = suggestion
+# CA1826: Do not use Enumerable methods on indexable collections. Instead use the collection directly
+dotnet_diagnostic.CA1826.severity = suggestion
+# CA1827: Do not use Count() or LongCount() when Any() can be used
+dotnet_diagnostic.CA1827.severity = suggestion
+# CA1829: Use Length/Count property instead of Count() when available
+dotnet_diagnostic.CA1829.severity = suggestion
+# CA1834: Consider using 'StringBuilder.Append(char)' when applicable
+dotnet_diagnostic.CA1834.severity = suggestion
 # CA2012: Use ValueTask correctly
 dotnet_diagnostic.CA2012.severity = suggestion
--- a/eng/tools/BaselineGenerator/Program.cs
+++ b/eng/tools/BaselineGenerator/Program.cs
@ -168,7 +168,7 @@ namespace PackageBaselineGenerator
                    foreach (var group in reader.NuspecReader.GetDependencyGroups())
                    {
                        // Don't bother generating empty ItemGroup elements.
-                        if (group.Packages.Count() == 0)
+                        if (!group.Packages.Any())
                        {
                            continue;
                        }
--- a/src/Components/Analyzers/test/Verifiers/DiagnosticVerifier.cs
+++ b/src/Components/Analyzers/test/Verifiers/DiagnosticVerifier.cs
@ -109,7 +109,7 @@ namespace TestHelper
        /// <param name="expectedResults">Diagnostic Results that should have appeared in the code</param>
        private static void VerifyDiagnosticResults(IEnumerable<Diagnostic> actualResults, DiagnosticAnalyzer analyzer, params DiagnosticResult[] expectedResults)
        {
-            int expectedCount = expectedResults.Count();
+            int expectedCount = expectedResults.Length;
            int actualCount = actualResults.Count();

            if (expectedCount != actualCount)
--- a/src/Components/WebAssembly/WebAssembly/src/Services/WebAssemblyConsoleLogger.cs
+++ b/src/Components/WebAssembly/WebAssembly/src/Services/WebAssemblyConsoleLogger.cs
@ -119,9 +119,9 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Services
            logBuilder.Append(GetLogLevelString(logLevel));
            logBuilder.Append(_loglevelPadding);
            logBuilder.Append(logName);
-            logBuilder.Append("[");
+            logBuilder.Append('[');
            logBuilder.Append(eventId);
-            logBuilder.Append("]");
+            logBuilder.Append(']');

            if (!string.IsNullOrEmpty(message))
            {
--- a/src/Components/WebView/WebView/src/QueryString.cs
+++ b/src/Components/WebView/WebView/src/QueryString.cs
@ -292,9 +292,9 @@ namespace Microsoft.AspNetCore.Components.WebView

        private static void AppendKeyValuePair(StringBuilder builder, string key, string? value, bool first)
        {
-            builder.Append(first ? "?" : "&");
+            builder.Append(first ? '?' : '&');
            builder.Append(UrlEncoder.Default.Encode(key));
-            builder.Append("=");
+            builder.Append('=');
            if (!string.IsNullOrEmpty(value))
            {
                builder.Append(UrlEncoder.Default.Encode(value));
--- a/src/FileProviders/Embedded/src/Manifest/ManifestParser.cs
+++ b/src/FileProviders/Embedded/src/Manifest/ManifestParser.cs
@ -143,7 +143,7 @@ namespace Microsoft.Extensions.FileProviders.Embedded.Manifest

        private static string EnsureText(XElement element)
        {
-            if (element.Elements().Count() == 0 &&
+            if (!element.Elements().Any() &&
                !element.IsEmpty &&
                element.Nodes().Count() == 1 &&
                element.FirstNode?.NodeType == XmlNodeType.Text)
--- a/src/Http/Headers/src/CookieHeaderValue.cs
+++ b/src/Http/Headers/src/CookieHeaderValue.cs
@ -94,7 +94,7 @@ namespace Microsoft.Net.Http.Headers
            var header = new StringBuilder();

            header.Append(_name.AsSpan());
-            header.Append("=");
+            header.Append('=');
            header.Append(_value.AsSpan());

            return header.ToString();
--- a/src/Http/Headers/src/SetCookieHeaderValue.cs
+++ b/src/Http/Headers/src/SetCookieHeaderValue.cs
@ -329,7 +329,7 @@ namespace Microsoft.Net.Http.Headers
        public void AppendToStringBuilder(StringBuilder builder)
        {
            builder.Append(_name.AsSpan());
-            builder.Append("=");
+            builder.Append('=');
            builder.Append(_value.AsSpan());

            if (Expires.HasValue)
@ -388,7 +388,7 @@ namespace Microsoft.Net.Http.Headers
            builder.Append(name.AsSpan());
            if (value != null)
            {
-                builder.Append("=");
+                builder.Append('=');
                builder.Append(value.AsSpan());
            }
        }
--- a/src/Http/Http.Abstractions/src/QueryString.cs
+++ b/src/Http/Http.Abstractions/src/QueryString.cs
@ -286,9 +286,9 @@ namespace Microsoft.AspNetCore.Http

        private static void AppendKeyValuePair(StringBuilder builder, string key, string? value, bool first)
        {
-            builder.Append(first ? "?" : "&");
+            builder.Append(first ? '?' : '&');
            builder.Append(UrlEncoder.Default.Encode(key));
-            builder.Append("=");
+            builder.Append('=');
            if (!string.IsNullOrEmpty(value))
            {
                builder.Append(UrlEncoder.Default.Encode(value));
--- a/src/Http/Routing/src/DefaultLinkGenerator.cs
+++ b/src/Http/Routing/src/DefaultLinkGenerator.cs
@ -480,14 +480,14 @@ namespace Microsoft.AspNetCore.Routing

                foreach (var kvp in values.OrderBy(kvp => kvp.Key))
                {
-                    builder.Append("\"");
+                    builder.Append('"');
                    builder.Append(kvp.Key);
-                    builder.Append("\"");
-                    builder.Append(":");
-                    builder.Append(" ");
-                    builder.Append("\"");
+                    builder.Append('"');
+                    builder.Append(':');
+                    builder.Append(' ');
+                    builder.Append('"');
                    builder.Append(kvp.Value);
-                    builder.Append("\"");
+                    builder.Append('"');
                    builder.Append(", ");
                }

--- a/src/Http/Routing/src/Patterns/RoutePatternParameterPart.cs
+++ b/src/Http/Routing/src/Patterns/RoutePatternParameterPart.cs
@ -80,14 +80,14 @@ namespace Microsoft.AspNetCore.Routing.Patterns
        internal override string DebuggerToString()
        {
            var builder = new StringBuilder();
-            builder.Append("{");
+            builder.Append('{');

            if (IsCatchAll)
            {
-                builder.Append("*");
+                builder.Append('*');
                if (!EncodeSlashes)
                {
-                    builder.Append("*");
+                    builder.Append('*');
                }
            }

@ -95,22 +95,22 @@ namespace Microsoft.AspNetCore.Routing.Patterns

            foreach (var constraint in ParameterPolicies)
            {
-                builder.Append(":");
+                builder.Append(':');
                builder.Append(constraint.ParameterPolicy);
            }

            if (Default != null)
            {
-                builder.Append("=");
+                builder.Append('=');
                builder.Append(Default);
            }

            if (IsOptional)
            {
-                builder.Append("?");
+                builder.Append('?');
            }

-            builder.Append("}");
+            builder.Append('}');
            return builder.ToString();
        }
    }
--- a/src/Http/Routing/src/Tree/LinkGenerationDecisionTree.cs
+++ b/src/Http/Routing/src/Tree/LinkGenerationDecisionTree.cs
@ -248,7 +248,7 @@ namespace Microsoft.AspNetCore.Routing.Tree
                {
                    matchesSb.Insert(0, branch);
                }
-                sb.Append(matchesSb.ToString());
+                sb.Append(matchesSb);
                sb.Append(" (Matches: ");
                sb.AppendJoin(", ", node.Matches.Select(m => m.Entry.RouteTemplate.TemplateText));
                sb.AppendLine(")");
--- a/src/Http/Routing/src/UriBuildingContext.cs
+++ b/src/Http/Routing/src/UriBuildingContext.cs
@ -111,7 +111,7 @@ namespace Microsoft.AspNetCore.Routing
            {
                if (_path.Length != 0)
                {
-                    _path.Append("/");
+                    _path.Append('/');
                }
            }

@ -124,7 +124,7 @@ namespace Microsoft.AspNetCore.Routing
            // This prevents the leading slash from PathString segments from being encoded.
            if (_path.Length == 0 && value.Length > 0 && value[0] == '/')
            {
-                _path.Append("/");
+                _path.Append('/');
                EncodeValue(value, 1, value.Length - 1, encodeSlashes);
            }
            else
@ -305,7 +305,7 @@ namespace Microsoft.AspNetCore.Routing
                while ((end = value.IndexOf('/', start, characterCount)) >= 0)
                {
                    _urlEncoder.Encode(PathWriter, value, start, end - start);
-                    _path.Append("/");
+                    _path.Append('/');

                    start = end + 1;
                    characterCount = length - start;
--- a/src/Http/Routing/tools/Swaggatherer/SwaggathererApplication.cs
+++ b/src/Http/Routing/tools/Swaggatherer/SwaggathererApplication.cs
@ -244,7 +244,7 @@ namespace Swaggatherer
                // We don't yet handle complex segments
                var part = template.Segments[i].Parts[0];

-                url.Append("/");
+                url.Append('/');
                url.Append(part.IsLiteral ? part.Text : GenerateParameterValue(part));
            }

--- a/src/Identity/Extensions.Core/src/Base32.cs
+++ b/src/Identity/Extensions.Core/src/Base32.cs
@ -46,7 +46,7 @@ namespace Microsoft.AspNetCore.Identity
            input = input.TrimEnd('=').ToUpperInvariant();
            if (input.Length == 0)
            {
-                return new byte[0];
+                return Array.Empty<byte>();
            }

            var output = new byte[input.Length * 5 / 8];
--- a/src/Identity/Specification.Tests/src/UserManagerSpecificationTests.cs
+++ b/src/Identity/Specification.Tests/src/UserManagerSpecificationTests.cs
@ -1826,7 +1826,7 @@ namespace Microsoft.AspNetCore.Identity.Test
            await manager.ConfirmEmailAsync(user, token);
            factors = await manager.GetValidTwoFactorProvidersAsync(user);
            Assert.NotNull(factors);
-            Assert.Equal(2, factors.Count());
+            Assert.Equal(2, factors.Count);
            IdentityResultAssert.IsSuccess(await manager.SetEmailAsync(user, null));
            factors = await manager.GetValidTwoFactorProvidersAsync(user);
            Assert.NotNull(factors);
@ -1835,7 +1835,7 @@ namespace Microsoft.AspNetCore.Identity.Test
            IdentityResultAssert.IsSuccess(await manager.ResetAuthenticatorKeyAsync(user));
            factors = await manager.GetValidTwoFactorProvidersAsync(user);
            Assert.NotNull(factors);
-            Assert.Equal(2, factors.Count());
+            Assert.Equal(2, factors.Count);
            Assert.Equal("Authenticator", factors[1]);
        }

--- a/src/Identity/UI/src/Areas/Identity/Pages/V4/Account/Manage/EnableAuthenticator.cshtml.cs
+++ b/src/Identity/UI/src/Areas/Identity/Pages/V4/Account/Manage/EnableAuthenticator.cshtml.cs
@ -182,12 +182,12 @@ namespace Microsoft.AspNetCore.Identity.UI.V4.Pages.Account.Manage.Internal
            int currentPosition = 0;
            while (currentPosition + 4 < unformattedKey.Length)
            {
-                result.Append(unformattedKey.Substring(currentPosition, 4)).Append(" ");
+                result.Append(unformattedKey.AsSpan(currentPosition, 4)).Append(' ');
                currentPosition += 4;
            }
            if (currentPosition < unformattedKey.Length)
            {
-                result.Append(unformattedKey.Substring(currentPosition));
+                result.Append(unformattedKey.AsSpan(currentPosition));
            }

            return result.ToString().ToLowerInvariant();
--- a/src/Identity/test/InMemory.Test/InMemoryStore.cs
+++ b/src/Identity/test/InMemory.Test/InMemoryStore.cs
@ -14,7 +14,7 @@ namespace Microsoft.AspNetCore.Identity.InMemory
    public class InMemoryStore<TUser, TRole> :
        InMemoryUserStore<TUser>,
        IUserRoleStore<TUser>,
-        IQueryableRoleStore<TRole>, 
+        IQueryableRoleStore<TRole>,
        IRoleClaimStore<TRole>
        where TRole : PocoRole
        where TUser : PocoUser
@ -72,7 +72,7 @@ namespace Microsoft.AspNetCore.Identity.InMemory
            {
                return Task.FromResult<IList<TUser>>(new List<TUser>());
            }
-            return Task.FromResult<IList<TUser>>(Users.Where(u => (u.Roles.Where(x => x.RoleId == role.Id).Count() > 0)).Select(x => x).ToList());
+            return Task.FromResult<IList<TUser>>(Users.Where(u => (u.Roles.Where(x => x.RoleId == role.Id).Any())).Select(x => x).ToList());
        }

        private readonly Dictionary<string, TRole> _roles = new Dictionary<string, TRole>();
--- a/src/Middleware/CORS/src/Infrastructure/CorsPolicy.cs
+++ b/src/Middleware/CORS/src/Infrastructure/CorsPolicy.cs
@ -161,16 +161,16 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
            builder.Append(SupportsCredentials);
            builder.Append(", Origins: {");
            builder.AppendJoin(",", Origins);
-            builder.Append("}");
+            builder.Append('}');
            builder.Append(", Methods: {");
            builder.AppendJoin(",", Methods);
-            builder.Append("}");
+            builder.Append('}');
            builder.Append(", Headers: {");
            builder.AppendJoin(",", Headers);
-            builder.Append("}");
+            builder.Append('}');
            builder.Append(", ExposedHeaders: {");
            builder.AppendJoin(",", ExposedHeaders);
-            builder.Append("}");
+            builder.Append('}');
            return builder.ToString();
        }

--- a/src/Middleware/CORS/src/Infrastructure/CorsResult.cs
+++ b/src/Middleware/CORS/src/Infrastructure/CorsResult.cs
@ -93,13 +93,13 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
            builder.Append(AllowedOrigin);
            builder.Append(", AllowExposedHeaders: {");
            builder.AppendJoin(",", AllowedExposedHeaders);
-            builder.Append("}");
+            builder.Append('}');
            builder.Append(", AllowHeaders: {");
            builder.AppendJoin(",", AllowedHeaders);
-            builder.Append("}");
+            builder.Append('}');
            builder.Append(", AllowMethods: {");
            builder.AppendJoin(",", AllowedMethods);
-            builder.Append("}");
+            builder.Append('}');
            return builder.ToString();
        }
    }
--- a/src/Middleware/Diagnostics.EntityFrameworkCore/src/DatabaseErrorPageMiddleware.cs
+++ b/src/Middleware/Diagnostics.EntityFrameworkCore/src/DatabaseErrorPageMiddleware.cs
@ -113,7 +113,7 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore
                        var contextType = _localDiagnostic.Value!.ContextType;
                        var details = await httpContext.GetContextDetailsAsync(contextType!, _logger);

-                        if (details != null && (details.PendingModelChanges || details.PendingMigrations.Count() > 0))
+                        if (details != null && (details.PendingModelChanges || details.PendingMigrations.Any()))
                        {
                            var page = new DatabaseErrorPage
                            {
--- a/src/Middleware/HealthChecks.EntityFrameworkCore/test/DbContextHealthCheckTest.cs
+++ b/src/Middleware/HealthChecks.EntityFrameworkCore/test/DbContextHealthCheckTest.cs
@ -39,7 +39,7 @@ namespace Microsoft.Extensions.Diagnostics.HealthChecks
            // Arrange
            var services = CreateServices(async (c, ct) =>
            {
-                return 0 < await c.Blogs.CountAsync();
+                return await c.Blogs.AnyAsync();
            });

            using (var scope = services.GetRequiredService<IServiceScopeFactory>().CreateScope())
@ -66,7 +66,7 @@ namespace Microsoft.Extensions.Diagnostics.HealthChecks
            // Arrange
            var services = CreateServices(async (c, ct) =>
            {
-                return 0 < await c.Blogs.CountAsync();
+                return await c.Blogs.AnyAsync();
            }, failureStatus: HealthStatus.Degraded);

            using (var scope = services.GetRequiredService<IServiceScopeFactory>().CreateScope())
@ -88,7 +88,7 @@ namespace Microsoft.Extensions.Diagnostics.HealthChecks
            // Arrange
            var services = CreateServices(async (c, ct) =>
            {
-                return 0 < await c.Blogs.CountAsync();
+                return await c.Blogs.AnyAsync();
            }, failureStatus: HealthStatus.Unhealthy);

            using (var scope = services.GetRequiredService<IServiceScopeFactory>().CreateScope())
@ -110,7 +110,7 @@ namespace Microsoft.Extensions.Diagnostics.HealthChecks
            // Arrange
            var services = CreateServices(async (c, ct) =>
            {
-                return 0 < await c.Blogs.CountAsync();
+                return await c.Blogs.AnyAsync();
            }, failureStatus: null);

            using (var scope = services.GetRequiredService<IServiceScopeFactory>().CreateScope())
--- a/src/Middleware/Session/src/NoOpSessionStore.cs
+++ b/src/Middleware/Session/src/NoOpSessionStore.cs
@ -21,7 +21,7 @@ namespace Microsoft.AspNetCore.Session

        public ICollection<EncodedKey> Keys { get; } = Array.Empty<EncodedKey>();

-        public ICollection<byte[]> Values { get; } = new byte[0][];
+        public ICollection<byte[]> Values { get; } = Array.Empty<byte[]>();

        public void Clear() { }

--- a/src/Mvc/Mvc.Abstractions/src/ModelBinding/ValueProviderResult.cs
+++ b/src/Mvc/Mvc.Abstractions/src/ModelBinding/ValueProviderResult.cs
@ -32,7 +32,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
        /// <summary>
        /// A <see cref="ValueProviderResult"/> that represents a lack of data.
        /// </summary>
-        public static ValueProviderResult None = new ValueProviderResult(new string[0]);
+        public static ValueProviderResult None = new ValueProviderResult(Array.Empty<string>());

        /// <summary>
        /// Creates a new <see cref="ValueProviderResult"/> using <see cref="CultureInfo.InvariantCulture"/>.
--- a/src/Mvc/Mvc.Core/src/MvcCoreLoggerExtensions.cs
+++ b/src/Mvc/Mvc.Core/src/MvcCoreLoggerExtensions.cs
@ -766,7 +766,7 @@ namespace Microsoft.AspNetCore.Mvc
                var routeKeys = action.RouteValues.Keys.ToArray();
                var routeValues = action.RouteValues.Values.ToArray();
                var stringBuilder = new StringBuilder();
-                stringBuilder.Append("{");
+                stringBuilder.Append('{');
                for (var i = 0; i < routeValues.Length; i++)
                {
                    if (i == routeValues.Length - 1)
@ -778,7 +778,7 @@ namespace Microsoft.AspNetCore.Mvc
                        stringBuilder.Append($"{routeKeys[i]} = \"{routeValues[i]}\", ");
                    }
                }
-                stringBuilder.Append("}");
+                stringBuilder.Append('}');

                if (action.RouteValues.TryGetValue("page", out var page) && page != null)
                {
--- a/src/Mvc/Mvc.TagHelpers/src/Cache/CacheTagKey.cs
+++ b/src/Mvc/Mvc.TagHelpers/src/Cache/CacheTagKey.cs
@ -306,7 +306,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers.Cache
            builder
                .Append(CacheKeyTokenSeparator)
                .Append(collectionName)
-                .Append("(");
+                .Append('(');

            for (var i = 0; i < values.Count; i++)
            {
@ -323,7 +323,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers.Cache
                    .Append(item.Value);
            }

-            builder.Append(")");
+            builder.Append(')');
        }

        private static void CombineCollectionHashCode(
--- a/src/Razor/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/src/ViewComponentTagHelperTargetExtension.cs
+++ b/src/Razor/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/src/ViewComponentTagHelperTargetExtension.cs
@ -170,9 +170,9 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X

        private void WriteTargetElementString(CodeWriter writer, TagHelperDescriptor tagHelper)
        {
-            Debug.Assert(tagHelper.TagMatchingRules.Count() == 1);
+            Debug.Assert(tagHelper.TagMatchingRules.Count == 1);

-            var rule = tagHelper.TagMatchingRules.First();
+            var rule = tagHelper.TagMatchingRules[0];

            writer.Write("[")
                .WriteStartMethodInvocation(HtmlTargetElementAttributeTypeName)
--- a/src/Razor/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X/src/ViewComponentTagHelperTargetExtension.cs
+++ b/src/Razor/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X/src/ViewComponentTagHelperTargetExtension.cs
@ -170,9 +170,9 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X

        private void WriteTargetElementString(CodeWriter writer, TagHelperDescriptor tagHelper)
        {
-            Debug.Assert(tagHelper.TagMatchingRules.Count() == 1);
+            Debug.Assert(tagHelper.TagMatchingRules.Count == 1);

-            var rule = tagHelper.TagMatchingRules.First();
+            var rule = tagHelper.TagMatchingRules[0];

            writer.Write("[")
                .WriteStartMethodInvocation(HtmlTargetElementAttributeTypeName)
--- a/src/Razor/Microsoft.AspNetCore.Mvc.Razor.Extensions/src/ViewComponentTagHelperTargetExtension.cs
+++ b/src/Razor/Microsoft.AspNetCore.Mvc.Razor.Extensions/src/ViewComponentTagHelperTargetExtension.cs
@ -170,9 +170,9 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions

        private void WriteTargetElementString(CodeWriter writer, TagHelperDescriptor tagHelper)
        {
-            Debug.Assert(tagHelper.TagMatchingRules.Count() == 1);
+            Debug.Assert(tagHelper.TagMatchingRules.Count == 1);

-            var rule = tagHelper.TagMatchingRules.First();
+            var rule = tagHelper.TagMatchingRules[0];

            writer.Write("[")
                .WriteStartMethodInvocation(HtmlTargetElementAttributeTypeName)
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentBindLoweringPass.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentBindLoweringPass.cs
@ -775,7 +775,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Components

        private static IntermediateToken GetAttributeContent(IntermediateNode node)
        {
-            var template = node.FindDescendantNodes<TemplateIntermediateNode>().FirstOrDefault();
+            var nodes = node.FindDescendantNodes<TemplateIntermediateNode>();
+            var template = nodes.Count > 0 ? nodes[0] : default;
            if (template != null)
            {
                // See comments in TemplateDiagnosticPass
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentEventHandlerLoweringPass.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentEventHandlerLoweringPass.cs
@ -242,7 +242,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Components

        private static IReadOnlyList<IntermediateToken> GetAttributeContent(IntermediateNode node)
        {
-            var template = node.FindDescendantNodes<TemplateIntermediateNode>().FirstOrDefault();
+            var nodes = node.FindDescendantNodes<TemplateIntermediateNode>();
+            var template = nodes.Count > 0 ? nodes[0] : default;
            if (template != null)
            {
                // See comments in TemplateDiagnosticPass
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentMarkupBlockPass.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentMarkupBlockPass.cs
@ -219,7 +219,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                    // Treat node with errors as non-HTML
                    _foundNonHtml = true;
                }
-                
+
                // Visit Children
                base.VisitDefault(node);

@ -277,7 +277,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                var isVoid = Legacy.ParserHelpers.VoidElements.Contains(node.TagName);
                var hasBodyContent = node.Body.Any();

-                Builder.Append("<");
+                Builder.Append('<');
                Builder.Append(node.TagName);

                foreach (var attribute in node.Attributes)
@ -290,7 +290,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                if (!hasBodyContent && isVoid)
                {
                    // void
-                    Builder.Append(">");
+                    Builder.Append('>');
                    return;
                }
                else if (!hasBodyContent)
@ -299,12 +299,12 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                    // add a close tag
                    Builder.Append("></");
                    Builder.Append(node.TagName);
-                    Builder.Append(">");
+                    Builder.Append('>');
                    return;
                }

                // start/end tag with body.
-                Builder.Append(">");
+                Builder.Append('>');

                foreach (var item in node.Body)
                {
@ -313,12 +313,12 @@ namespace Microsoft.AspNetCore.Razor.Language.Components

                Builder.Append("</");
                Builder.Append(node.TagName);
-                Builder.Append(">");
+                Builder.Append('>');
            }

            public override void VisitHtmlAttribute(HtmlAttributeIntermediateNode node)
            {
-                Builder.Append(" ");
+                Builder.Append(' ');
                Builder.Append(node.AttributeName);

                if (node.Children.Count == 0)
@ -332,7 +332,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                // Visit Children
                base.VisitDefault(node);

-                Builder.Append("\"");
+                Builder.Append('"');
            }

            public override void VisitHtmlAttributeValue(HtmlAttributeValueIntermediateNode node)
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorIntermediateNodeLoweringPhase.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorIntermediateNodeLoweringPhase.cs
@ -347,7 +347,7 @@ namespace Microsoft.AspNetCore.Razor.Language
                    _builder.Add(new DirectiveTokenIntermediateNode()
                    {
                        Content = addTagHelperChunkGenerator.LookupText,
-                        DirectiveToken = CSharpCodeParser.AddTagHelperDirectiveDescriptor.Tokens.First(),
+                        DirectiveToken = CSharpCodeParser.AddTagHelperDirectiveDescriptor.Tokens[0],
                        Source = BuildSourceSpanFromNode(node),
                    });

@ -385,7 +385,7 @@ namespace Microsoft.AspNetCore.Razor.Language
                    _builder.Add(new DirectiveTokenIntermediateNode()
                    {
                        Content = removeTagHelperChunkGenerator.LookupText,
-                        DirectiveToken = CSharpCodeParser.RemoveTagHelperDirectiveDescriptor.Tokens.First(),
+                        DirectiveToken = CSharpCodeParser.RemoveTagHelperDirectiveDescriptor.Tokens[0],
                        Source = BuildSourceSpanFromNode(node),
                    });

@ -423,7 +423,7 @@ namespace Microsoft.AspNetCore.Razor.Language
                    _builder.Add(new DirectiveTokenIntermediateNode()
                    {
                        Content = tagHelperPrefixChunkGenerator.Prefix,
-                        DirectiveToken = CSharpCodeParser.TagHelperPrefixDirectiveDescriptor.Tokens.First(),
+                        DirectiveToken = CSharpCodeParser.TagHelperPrefixDirectiveDescriptor.Tokens[0],
                        Source = BuildSourceSpanFromNode(node),
                    });

@ -1019,7 +1019,8 @@ namespace Microsoft.AspNetCore.Razor.Language

                IReadOnlyList<SyntaxNode> children = node.ChildNodes();
                var position = node.Position;
-                if (children.FirstOrDefault() is MarkupBlockSyntax markupBlock &&
+                if (children.Count > 0 &&
+                    children[0] is MarkupBlockSyntax markupBlock &&
                    markupBlock.Children.Count == 2 &&
                    markupBlock.Children[0] is MarkupTextLiteralSyntax &&
                    markupBlock.Children[1] is MarkupEphemeralTextLiteralSyntax)
@ -1970,7 +1971,8 @@ namespace Microsoft.AspNetCore.Razor.Language

                IReadOnlyList<SyntaxNode> children = node.ChildNodes();
                var position = node.Position;
-                if (children.FirstOrDefault() is MarkupBlockSyntax markupBlock &&
+                if (children.Count > 0 &&
+                    children[0] is MarkupBlockSyntax markupBlock &&
                    markupBlock.Children.Count == 2 &&
                    markupBlock.Children[0] is MarkupTextLiteralSyntax &&
                    markupBlock.Children[1] is MarkupEphemeralTextLiteralSyntax)
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/MethodDeclarationIntermediateNode.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/MethodDeclarationIntermediateNode.cs
@ -46,11 +46,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Intermediate
            for (var i = 0; i <parameter.Modifiers.Count; i++)
            {
                builder.Append(parameter.Modifiers[i]);
-                builder.Append(" ");
+                builder.Append(' ');
            }

            builder.Append(parameter.TypeName);
-            builder.Append(" ");
+            builder.Append(' ');

            builder.Append(parameter.ParameterName);

--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/AddTagHelperChunkGenerator.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/AddTagHelperChunkGenerator.cs
@ -64,20 +64,20 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
        {
            var builder = new StringBuilder("AddTagHelper:{");
            builder.Append(LookupText);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(DirectiveText);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(TypePattern);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(AssemblyName);
-            builder.Append("}");
+            builder.Append('}');

            if (Diagnostics.Count > 0)
            {
                builder.Append(" [");
                var ids = string.Join(", ", Diagnostics.Select(diagnostic => $"{diagnostic.Id}{diagnostic.Span}"));
                builder.Append(ids);
-                builder.Append("]");
+                builder.Append(']');
            }

            return builder.ToString();
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/CSharpCodeParser.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/CSharpCodeParser.cs
@ -46,10 +46,6 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                builder.Description = Resources.TagHelperPrefixDirective_Description;
            });

-        internal static readonly IEnumerable<DirectiveDescriptor> DefaultDirectiveDescriptors = new DirectiveDescriptor[]
-        {
-        };
-
        internal static ISet<string> DefaultKeywords = new HashSet<string>()
        {
            SyntaxConstants.CSharp.TagHelperPrefixKeyword,
@ -912,11 +908,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy

        private void SetupDirectiveParsers(IEnumerable<DirectiveDescriptor> directiveDescriptors)
        {
-            var allDirectives = directiveDescriptors.Concat(DefaultDirectiveDescriptors).ToList();
-
-            for (var i = 0; i < allDirectives.Count; i++)
+            foreach (var directiveDescriptor in directiveDescriptors)
            {
-                var directiveDescriptor = allDirectives[i];
                CurrentKeywords.Add(directiveDescriptor.Directive);
                MapDirectives((builder, transition) => ParseExtensibleDirective(builder, transition, directiveDescriptor), directiveDescriptor.Directive);
            }
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/DirectiveTokenChunkGenerator.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/DirectiveTokenChunkGenerator.cs
@ -38,11 +38,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
        {
            var builder = new StringBuilder("DirectiveToken {");
            builder.Append(Descriptor.Name);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(Descriptor.Kind);
            builder.Append(";Opt:");
            builder.Append(Descriptor.Optional);
-            builder.Append("}");
+            builder.Append('}');

            return builder.ToString();
        }
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/RemoveTagHelperChunkGenerator.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/RemoveTagHelperChunkGenerator.cs
@ -64,20 +64,20 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
        {
            var builder = new StringBuilder("RemoveTagHelper:{");
            builder.Append(LookupText);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(DirectiveText);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(TypePattern);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(AssemblyName);
-            builder.Append("}");
+            builder.Append('}');

            if (Diagnostics.Count > 0)
            {
                builder.Append(" [");
                var ids = string.Join(", ", Diagnostics.Select(diagnostic => $"{diagnostic.Id}{diagnostic.Span}"));
                builder.Append(ids);
-                builder.Append("]");
+                builder.Append(']');
            }

            return builder.ToString();
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/TagHelperParseTreeRewriter.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/TagHelperParseTreeRewriter.cs
@ -49,7 +49,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
        {
            // Internal for testing.
            // Null characters are invalid markup for HTML attribute values.
-            internal const string InvalidAttributeValueMarker = "\0";
+            internal const char InvalidAttributeValueMarker = '\0';

            private readonly RazorSourceDocument _source;
            private readonly string _tagHelperPrefix;
@ -759,7 +759,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                    {
                        if (AllowedChildren != null && _prefixedAllowedChildren == null)
                        {
-                            Debug.Assert(Info.BindingResult.Descriptors.Count() >= 1);
+                            Debug.Assert(Info.BindingResult.Descriptors.Any());

                            _prefixedAllowedChildren = AllowedChildren.Select(allowedChild => _tagHelperPrefix + allowedChild).ToList();
                        }
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/TagHelperPrefixDirectiveChunkGenerator.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Legacy/TagHelperPrefixDirectiveChunkGenerator.cs
@ -49,19 +49,19 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
        {
            var builder = new StringBuilder("TagHelperPrefix:{");
            builder.Append(Prefix);
-            builder.Append(";");
+            builder.Append(';');
            builder.Append(DirectiveText);
-            builder.Append("}");
+            builder.Append('}');

            if (Diagnostics.Count > 0)
            {
                builder.Append(" [");
                var ids = string.Join(", ", Diagnostics.Select(diagnostic => $"{diagnostic.Id}{diagnostic.Span}"));
                builder.Append(ids);
-                builder.Append("]");
+                builder.Append(']');
            }

            return builder.ToString();
        }
    }
-}
+}
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorDiagnostic.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorDiagnostic.cs
@ -7,8 +7,8 @@ namespace Microsoft.AspNetCore.Razor.Language
 {
    public abstract class RazorDiagnostic : IEquatable<RazorDiagnostic>, IFormattable
    {
-        internal static readonly RazorDiagnostic[] EmptyArray = new RazorDiagnostic[0];
-        internal static readonly object[] EmptyArgs = new object[0];
+        internal static readonly RazorDiagnostic[] EmptyArray = Array.Empty<RazorDiagnostic>();
+        internal static readonly object[] EmptyArgs = Array.Empty<object>();

        public abstract string Id { get; }

--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorSourceDocument.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorSourceDocument.cs
@ -15,7 +15,7 @@ namespace Microsoft.AspNetCore.Razor.Language
    {
        internal const int LargeObjectHeapLimitInChars = 40 * 1024; // 40K Unicode chars is 80KB which is less than the large object heap limit.

-        internal static readonly RazorSourceDocument[] EmptyArray = new RazorSourceDocument[0];
+        internal static readonly RazorSourceDocument[] EmptyArray = Array.Empty<RazorSourceDocument>();

        /// <summary>
        /// Gets the encoding of the text in the original source document.
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Syntax/SyntaxSerializer.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Syntax/SyntaxSerializer.cs
@ -197,11 +197,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Syntax

                var builder = new StringBuilder("Directive:{");
                builder.Append(node.DirectiveDescriptor.Directive);
-                builder.Append(";");
+                builder.Append(';');
                builder.Append(node.DirectiveDescriptor.Kind);
-                builder.Append(";");
+                builder.Append(';');
                builder.Append(node.DirectiveDescriptor.Usage);
-                builder.Append("}");
+                builder.Append('}');

                var diagnostics = node.GetDiagnostics();
                if (diagnostics.Length > 0)
@ -209,7 +209,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Syntax
                    builder.Append(" [");
                    var ids = string.Join(", ", diagnostics.Select(diagnostic => $"{diagnostic.Id}{diagnostic.Span}"));
                    builder.Append(ids);
-                    builder.Append("]");
+                    builder.Append(']');
                }

                WriteSeparator();
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/DefaultRazorTagHelperBinderPhaseTest.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/DefaultRazorTagHelperBinderPhaseTest.cs
@ -344,7 +344,7 @@ namespace Microsoft.AspNetCore.Razor.Language

            var formTagHelper = Assert.Single(tagHelperNodes);
            Assert.Equal("form", formTagHelper.TagHelperInfo.TagName);
-            Assert.Equal(2, formTagHelper.TagHelperInfo.BindingResult.Mappings[descriptor].Count());
+            Assert.Equal(2, formTagHelper.TagHelperInfo.BindingResult.Mappings[descriptor].Count);
        }

        [Fact]
@ -398,7 +398,7 @@ namespace Microsoft.AspNetCore.Razor.Language

            var formTagHelper = Assert.Single(tagHelperNodes);
            Assert.Equal("form", formTagHelper.TagHelperInfo.TagName);
-            Assert.Equal(2, formTagHelper.TagHelperInfo.BindingResult.Mappings[descriptor].Count());
+            Assert.Equal(2, formTagHelper.TagHelperInfo.BindingResult.Mappings[descriptor].Count);
        }

        [Fact]
@ -653,7 +653,7 @@ namespace Microsoft.AspNetCore.Razor.Language
                    },
                    {
                        $@"
-@tagHelperPrefix 
+@tagHelperPrefix
@addTagHelper Microsoft.AspNetCore.Razor.TagHelpers.ValidPlain*, {AssemblyA}
@addTagHelper Microsoft.AspNetCore.Razor.TagHelpers.ValidInherited*, {AssemblyA}",
                        null
@ -858,7 +858,7 @@ namespace Microsoft.AspNetCore.Razor.Language
            visitor.Visit(syntaxTree.Root);

            // Assert
-            Assert.Equal(expected.Count(), visitor.Matches.Count());
+            Assert.Equal(expected.Length, visitor.Matches.Count);

            foreach (var expectedDescriptor in expected)
            {
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/Legacy/TagHelperParseTreeRewriterTest.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/Legacy/TagHelperParseTreeRewriterTest.cs
@ -18,7 +18,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                Func<string, string, KeyValuePair<string, string>> kvp =
                    (key, value) => new KeyValuePair<string, string>(key, value);
                var empty = Enumerable.Empty<KeyValuePair<string, string>>();
-                var csharp = TagHelperParseTreeRewriter.Rewriter.InvalidAttributeValueMarker;
+                var csharp = TagHelperParseTreeRewriter.Rewriter.InvalidAttributeValueMarker.ToString();

                // documentContent, expectedPairs
                return new TheoryData<string, IEnumerable<KeyValuePair<string, string>>>
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TagHelperDescriptorComparerTest.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TagHelperDescriptorComparerTest.cs
@ -134,7 +134,7 @@ namespace Microsoft.AspNetCore.Razor.Language
            var hashes = new HashSet<int>(tagHelpers.Select(t => t.GetHashCode()));

            // Assert
-            Assert.Equal(hashes.Count(), tagHelpers.Count);
+            Assert.Equal(hashes.Count, tagHelpers.Count);
        }

        [Fact]
@ -158,7 +158,7 @@ namespace Microsoft.AspNetCore.Razor.Language

            // Assert
            // Only 1 batch of taghelpers should remain after we filter by hash
-            Assert.Equal(hashes.Count(), tagHelpersPerBatch);
+            Assert.Equal(hashes.Count, tagHelpersPerBatch);
        }

        private static TagHelperDescriptor CreateTagHelperDescriptor(
--- a/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentTagHelperDescriptorProvider.cs
+++ b/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentTagHelperDescriptorProvider.cs
@ -288,7 +288,7 @@ namespace Microsoft.CodeAnalysis.Razor
            builder.TagMatchingRule(r =>
            {
                r.TagName = attribute.Name;
-                r.ParentTag = component.TagMatchingRules.First().TagName;
+                r.ParentTag = component.TagMatchingRules[0].TagName;
            });

            if (attribute.IsParameterizedChildContentProperty())
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common/Language/Legacy/SyntaxNodeWriter.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common/Language/Legacy/SyntaxNodeWriter.cs
@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

 using System;
--- a/src/Razor/tools/RazorSyntaxGenerator/SourceWriter.cs
+++ b/src/Razor/tools/RazorSyntaxGenerator/SourceWriter.cs
@ -2087,7 +2087,7 @@ namespace RazorSyntaxGenerator

            var minimalFactoryfields = new HashSet<Field>(DetermineMinimalFactoryFields(nd));

-            if (withStringNames && minimalFactoryfields.Count(f => IsRequiredFactoryField(nd, f) && CanAutoConvertFromString(f)) == 0)
+            if (withStringNames && !minimalFactoryfields.Any(f => IsRequiredFactoryField(nd, f) && CanAutoConvertFromString(f)))
                return; // no string-name overload necessary

            WriteLine();
--- a/src/Security/Authentication/Negotiate/src/Internal/ReflectedNegotiateState.cs
+++ b/src/Security/Authentication/Negotiate/src/Internal/ReflectedNegotiateState.cs
@ -36,7 +36,7 @@ namespace Microsoft.AspNetCore.Authentication.Negotiate
            var ntAuthType = secAssembly.GetType("System.Net.NTAuthentication", throwOnError: true)!;
            _constructor = ntAuthType.GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance).First();
            _getOutgoingBlob = ntAuthType.GetMethods(BindingFlags.NonPublic | BindingFlags.Instance).Where(info =>
-                info.Name.Equals("GetOutgoingBlob") && info.GetParameters().Count() == 3).Single();
+                info.Name.Equals("GetOutgoingBlob") && info.GetParameters().Length == 3).Single();
            _isCompleted = ntAuthType.GetMethods(BindingFlags.NonPublic | BindingFlags.Instance).Where(info =>
                info.Name.Equals("get_IsCompleted")).Single();
            _protocol = ntAuthType.GetMethods(BindingFlags.NonPublic | BindingFlags.Instance).Where(info =>
--- a/src/Security/Authentication/test/CertificateTests.cs
+++ b/src/Security/Authentication/test/CertificateTests.cs
@ -285,7 +285,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            var response = await server.CreateClient().GetAsync("https://example.com/");
            Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
        }
-        
+
        [Fact]
        public async Task VerifyValidationFailureCanBeHandled()
        {
@ -489,7 +489,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            if (!string.IsNullOrEmpty(Certificates.SelfSignedValidWithNoEku.SubjectName.Name))
            {
                actual = responseAsXml.Elements("claim").Where(claim => claim.Attribute("Type").Value == ClaimTypes.X500DistinguishedName);
-                if (actual.Count() > 0)
+                if (actual.Any())
                {
                    Assert.Single(actual);
                    Assert.Equal(Certificates.SelfSignedValidWithNoEku.SubjectName.Name, actual.First().Value);
@ -499,7 +499,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            if (!string.IsNullOrEmpty(Certificates.SelfSignedValidWithNoEku.SerialNumber))
            {
                actual = responseAsXml.Elements("claim").Where(claim => claim.Attribute("Type").Value == ClaimTypes.SerialNumber);
-                if (actual.Count() > 0)
+                if (actual.Any())
                {
                    Assert.Single(actual);
                    Assert.Equal(Certificates.SelfSignedValidWithNoEku.SerialNumber, actual.First().Value);
@ -509,7 +509,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            if (!string.IsNullOrEmpty(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.DnsName, false)))
            {
                actual = responseAsXml.Elements("claim").Where(claim => claim.Attribute("Type").Value == ClaimTypes.Dns);
-                if (actual.Count() > 0)
+                if (actual.Any())
                {
                    Assert.Single(actual);
                    Assert.Equal(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.DnsName, false), actual.First().Value);
@ -519,7 +519,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            if (!string.IsNullOrEmpty(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.EmailName, false)))
            {
                actual = responseAsXml.Elements("claim").Where(claim => claim.Attribute("Type").Value == ClaimTypes.Email);
-                if (actual.Count() > 0)
+                if (actual.Any())
                {
                    Assert.Single(actual);
                    Assert.Equal(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.EmailName, false), actual.First().Value);
@ -529,7 +529,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            if (!string.IsNullOrEmpty(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.SimpleName, false)))
            {
                actual = responseAsXml.Elements("claim").Where(claim => claim.Attribute("Type").Value == ClaimTypes.Name);
-                if (actual.Count() > 0)
+                if (actual.Any())
                {
                    Assert.Single(actual);
                    Assert.Equal(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.SimpleName, false), actual.First().Value);
@ -539,7 +539,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            if (!string.IsNullOrEmpty(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.UpnName, false)))
            {
                actual = responseAsXml.Elements("claim").Where(claim => claim.Attribute("Type").Value == ClaimTypes.Upn);
-                if (actual.Count() > 0)
+                if (actual.Any())
                {
                    Assert.Single(actual);
                    Assert.Equal(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.UpnName, false), actual.First().Value);
@ -549,7 +549,7 @@ namespace Microsoft.AspNetCore.Authentication.Certificate.Test
            if (!string.IsNullOrEmpty(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.UrlName, false)))
            {
                actual = responseAsXml.Elements("claim").Where(claim => claim.Attribute("Type").Value == ClaimTypes.Uri);
-                if (actual.Count() > 0)
+                if (actual.Any())
                {
                    Assert.Single(actual);
                    Assert.Equal(Certificates.SelfSignedValidWithNoEku.GetNameInfo(X509NameType.UrlName, false), actual.First().Value);
--- a/src/Servers/HttpSys/src/RequestProcessing/ResponseBody.cs
+++ b/src/Servers/HttpSys/src/RequestProcessing/ResponseBody.cs
@ -210,7 +210,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
            else if (!hasData && !addTrailers)
            {
                // No data
-                dataChunks = new HttpApiTypes.HTTP_DATA_CHUNK[0];
+                dataChunks = Array.Empty<HttpApiTypes.HTTP_DATA_CHUNK>();
                return pins;
            }

--- a/src/Servers/Kestrel/Core/src/Middleware/Internal/LoggingStream.cs
+++ b/src/Servers/Kestrel/Core/src/Middleware/Internal/LoggingStream.cs
@ -148,9 +148,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal

            var builder = new StringBuilder();
            builder.Append(method);
-            builder.Append("[");
+            builder.Append('[');
            builder.Append(buffer.Length);
-            builder.Append("]");
+            builder.Append(']');

            if (buffer.Length > 0)
            {
@ -163,12 +163,12 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal
            for (int i = 0; i < buffer.Length; i++)
            {
                builder.Append(buffer[i].ToString("X2", CultureInfo.InvariantCulture));
-                builder.Append(" ");
+                builder.Append(' ');

                var bufferChar = (char)buffer[i];
                if (char.IsControl(bufferChar))
                {
-                    charBuilder.Append(".");
+                    charBuilder.Append('.');
                }
                else
                {
@ -178,7 +178,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal
                if ((i + 1) % 16 == 0)
                {
                    builder.Append("  ");
-                    builder.Append(charBuilder.ToString());
+                    builder.Append(charBuilder);
                    if (i != buffer.Length - 1)
                    {
                        builder.AppendLine();
@ -187,8 +187,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal
                }
                else if ((i + 1) % 8 == 0)
                {
-                    builder.Append(" ");
-                    charBuilder.Append(" ");
+                    builder.Append(' ');
+                    charBuilder.Append(' ');
                }
            }

@ -206,7 +206,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal
                }

                builder.Append(new string(' ', padLength));
-                builder.Append(charBuilder.ToString());
+                builder.Append(charBuilder);
            }

            _logger.LogDebug(builder.ToString());
--- a/src/Servers/Kestrel/shared/KnownHeaders.cs
+++ b/src/Servers/Kestrel/shared/KnownHeaders.cs
@ -350,7 +350,7 @@ namespace CodeGenerator

        static string AppendSwitchSection(int length, IList<KnownHeader> values)
        {
-            var useVarForFirstTerm = values.Count() > 1 && values.Select(h => h.FirstNameIgnoreCaseSegment()).Distinct().Count() == 1;
+            var useVarForFirstTerm = values.Count > 1 && values.Select(h => h.FirstNameIgnoreCaseSegment()).Distinct().Count() == 1;
            var firstTermVarExpression = values.Select(h => h.FirstNameIgnoreCaseSegment()).FirstOrDefault();
            var firstTermVar = $"firstTerm{length}";

@ -1188,7 +1188,7 @@ $@"        private void Clear(long bitsToClear)
                                return;
                            }}")}
                        }}
-                        {(hi.Index + 1 < loop.Headers.Count() ? $"goto case {hi.Index + 1};" : "return;")}")}
+                        {(hi.Index + 1 < loop.Headers.Length ? $"goto case {hi.Index + 1};" : "return;")}")}
                    default:
                        return;
                }}
@ -1272,7 +1272,7 @@ $@"        private void Clear(long bitsToClear)
                {{{Each(loop.Headers.Where(header => header.Identifier != "ContentLength"), header => $@"
                    case {header.Index}:
                        goto Header{header.Identifier};")}
-                    {(!loop.ClassName.Contains("Trailers") ? $@"case {loop.Headers.Count() - 1}:
+                    {(!loop.ClassName.Contains("Trailers") ? $@"case {loop.Headers.Length - 1}:
                        goto HeaderContentLength;" : "")}
                    default:
                        goto ExtraHeaders;
@ -1286,12 +1286,12 @@ $@"        private void Clear(long bitsToClear)
                        ")}_next = {header.Index + 1};
                        return true;
                    }}")}
-                {(!loop.ClassName.Contains("Trailers") ? $@"HeaderContentLength: // case {loop.Headers.Count() - 1}
+                {(!loop.ClassName.Contains("Trailers") ? $@"HeaderContentLength: // case {loop.Headers.Length - 1}
                    if (_collection._contentLength.HasValue)
                    {{
                        _current = new KeyValuePair<string, StringValues>(HeaderNames.ContentLength, HeaderUtilities.FormatNonNegativeInt64(_collection._contentLength.Value));
                        {(loop.ClassName.Contains("Request") ? "" : @"_currentKnownType = KnownHeaderType.ContentLength;
-                        ")}_next = {loop.Headers.Count()};
+                        ")}_next = {loop.Headers.Length};
                        return true;
                    }}" : "")}
                ExtraHeaders:
--- a/src/Shared/Http2cat/Http2Utilities.cs
+++ b/src/Shared/Http2cat/Http2Utilities.cs
@ -119,7 +119,7 @@ namespace Microsoft.AspNetCore.Http2Cat
        public static readonly byte[] _helloBytes = Encoding.ASCII.GetBytes("hello");
        public static readonly byte[] _worldBytes = Encoding.ASCII.GetBytes("world");
        public static readonly byte[] _helloWorldBytes = Encoding.ASCII.GetBytes("hello, world");
-        public static readonly byte[] _noData = new byte[0];
+        public static readonly byte[] _noData = Array.Empty<byte>();
        public static readonly byte[] _maxData = Encoding.ASCII.GetBytes(new string('a', Http2PeerSettings.MinAllowedMaxFrameSize));

        internal readonly Http2PeerSettings _clientSettings = new Http2PeerSettings();
--- a/src/Shared/HttpSys/NativeInterop/SocketAddress.cs
+++ b/src/Shared/HttpSys/NativeInterop/SocketAddress.cs
@ -28,7 +28,7 @@ namespace Microsoft.AspNetCore.HttpSys.Internal
        private const int NumberOfIPv6Labels = 8;
        // Lower case hex, no leading zeros
        private const string IPv6NumberFormat = "{0:x}";
-        private const string IPv6StringSeparator = ":";
+        private const char IPv6StringSeparator = ':';
        private const string IPv4StringFormat = "{0:d}.{1:d}.{2:d}.{3:d}";

        internal const int IPv6AddressSize = 28;
@ -206,7 +206,7 @@ namespace Microsoft.AspNetCore.HttpSys.Internal
            {
                if (i > WriteableOffset)
                {
-                    bytes.Append(",");
+                    bytes.Append(',');
                }
                bytes.Append(this[i].ToString(NumberFormatInfo.InvariantInfo));
            }
--- a/src/Shared/HttpSys/RequestProcessing/HeaderParser.cs
+++ b/src/Shared/HttpSys/RequestProcessing/HeaderParser.cs
@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

+using System;
 using System.Collections.Generic;
 using Microsoft.Extensions.Primitives;

@ -8,7 +9,7 @@ namespace Microsoft.AspNetCore.HttpSys.Internal
 {
    internal static class HeaderParser
    {
-        internal static IEnumerable<string> Empty = new string[0];
+        internal static IEnumerable<string> Empty = Array.Empty<string>();

        // Split on commas, except in quotes
        internal static IEnumerable<string> SplitValues(StringValues values)
--- a/src/Shared/StackTrace/StackFrame/MethodDisplayInfo.cs
+++ b/src/Shared/StackTrace/StackFrame/MethodDisplayInfo.cs
@ -37,19 +37,19 @@ namespace Microsoft.Extensions.StackTrace.Sources
            {
                builder
                    .Append(DeclaringTypeName)
-                    .Append(".");
+                    .Append('.');
            }

            builder.Append(Name);
            builder.Append(GenericArguments);

-            builder.Append("(");
+            builder.Append('(');
            builder.AppendJoin(", ", Parameters.Select(p => p.ToString()));
-            builder.Append(")");
+            builder.Append(')');

            if (!string.IsNullOrEmpty(SubMethod))
            {
-                builder.Append("+");
+                builder.Append('+');
                builder.Append(SubMethod);
                builder.Append("()");
            }
--- a/src/Shared/StackTrace/StackFrame/ParameterDisplayInfo.cs
+++ b/src/Shared/StackTrace/StackFrame/ParameterDisplayInfo.cs
@ -21,11 +21,11 @@ namespace Microsoft.Extensions.StackTrace.Sources
            {
                builder
                    .Append(Prefix)
-                    .Append(" ");
+                    .Append(' ');
            }

            builder.Append(Type);
-            builder.Append(" ");
+            builder.Append(' ');
            builder.Append(Name);

            return builder.ToString();
--- a/src/SignalR/server/SignalR/test/HubConnectionHandlerTests.cs
+++ b/src/SignalR/server/SignalR/test/HubConnectionHandlerTests.cs
@ -4338,8 +4338,8 @@ namespace Microsoft.AspNetCore.SignalR.Tests
                    var messages = await messagePromise;

                    // add one because this includes the completion
-                    Assert.Equal(phrases.Count() + 1, messages.Count);
-                    for (var i = 0; i < phrases.Count(); i++)
+                    Assert.Equal(phrases.Length + 1, messages.Count);
+                    for (var i = 0; i < phrases.Length; i++)
                    {
                        Assert.Equal("echo:" + phrases[i], ((StreamItemMessage)messages[i]).Item);
                    }
--- a/src/Tools/Shared/TestHelpers/TemporaryCSharpProject.cs
+++ b/src/Tools/Shared/TestHelpers/TemporaryCSharpProject.cs
@ -75,7 +75,7 @@ namespace Microsoft.Extensions.Tools.Internal
        public TemporaryCSharpProject WithItem(ItemSpec item)
        {
            var sb = new StringBuilder("<");
-            sb.Append(item.Name).Append(" ");
+            sb.Append(item.Name).Append(' ');
            if (item.Include != null) sb.Append(" Include=\"").Append(item.Include).Append('"');
            if (item.Remove != null) sb.Append(" Remove=\"").Append(item.Remove).Append('"');
            if (item.Update != null) sb.Append(" Update=\"").Append(item.Update).Append('"');