Fix breaking change

src/Config/ChainedBuilderExtensions.cs

@@ -0,0 +1,35 @@
+// 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;
+
+namespace Microsoft.Extensions.Configuration
+{
+    /// <summary>
+    /// IConfigurationBuilder extension methods for the chaind configuration provider.
+    /// </summary>
+    public static class ChainedBuilderExtensions
+    {
+        /// <summary>
+        /// Adds an existing configuration to <paramref name="configurationBuilder"/>.
+        /// </summary>
+        /// <param name="configurationBuilder">The <see cref="IConfigurationBuilder"/> to add to.</param>
+        /// <param name="config">The <see cref="IConfiguration"/> to add.</param>
+        /// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
+        public static IConfigurationBuilder AddConfiguration(this IConfigurationBuilder configurationBuilder, IConfiguration config)
+        {
+            if (configurationBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(configurationBuilder));
+            }
+            if (config == null)
+            {
+                throw new ArgumentNullException(nameof(config));
+            }
+
+            configurationBuilder.Add(new ChainedConfigurationSource { Configuration = config });
+            return configurationBuilder;
+        }
+    }
+}

src/Config/ChainedConfigurationSource.cs

@@ -19,8 +19,6 @@ namespace Microsoft.Extensions.Configuration
         /// <param name="builder">The <see cref="IConfigurationBuilder"/>.</param>
         /// <returns>A <see cref="ChainedConfigurationProvider"/></returns>
         public IConfigurationProvider Build(IConfigurationBuilder builder)
-        {
-            return new ChainedConfigurationProvider(this);
-        }
+            => new ChainedConfigurationProvider(this);
     }
 }

src/Config/MemoryConfigurationBuilderExtensions.cs

@@ -8,31 +8,10 @@ using Microsoft.Extensions.Configuration.Memory;
 namespace Microsoft.Extensions.Configuration
 {
     /// <summary>
-    /// IConfigurationBuilder extension methods.
+    /// IConfigurationBuilder extension methods for the MemoryConfigurationProvider.
     /// </summary>
-    public static class ConfigurationBuilderExtensions
+    public static class MemoryConfigurationBuilderExtensions
     {
-        /// <summary>
-        /// Adds an existing configuration to <paramref name="configurationBuilder"/>.
-        /// </summary>
-        /// <param name="configurationBuilder">The <see cref="IConfigurationBuilder"/> to add to.</param>
-        /// <param name="config">The <see cref="IConfiguration"/> to add.</param>
-        /// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
-        public static IConfigurationBuilder AddConfiguration(this IConfigurationBuilder configurationBuilder, IConfiguration config)
-        {
-            if (configurationBuilder == null)
-            {
-                throw new ArgumentNullException(nameof(configurationBuilder));
-            }
-            if (config == null)
-            {
-                throw new ArgumentNullException(nameof(config));
-            }
-
-            configurationBuilder.Add(new ChainedConfigurationSource { Configuration = config });
-            return configurationBuilder;
-        }
-
         /// <summary>
         /// Adds the memory configuration provider to <paramref name="configurationBuilder"/>.
         /// </summary>
@@ -68,4 +47,4 @@ namespace Microsoft.Extensions.Configuration
             return configurationBuilder;
         }
     }
-}
+}