Use C# 6 string interpolation feature

Provides cleanup in logging and removes calls to String.Format

src/Microsoft.AspNet.DataProtection/AuthenticatedEncryption/CngCbcAuthenticatedEncryptionOptions.cs

@@ -113,7 +113,7 @@ namespace Microsoft.AspNet.DataProtection.AuthenticatedEncryption
 
             if (logger.IsVerboseLevelEnabled())
             {
-                logger.LogVerbose("Opening CNG algorithm '{0}' from provider '{1}' with HMAC.", HashAlgorithm, HashAlgorithmProvider);
+                logger.LogVerboseF($"Opening CNG algorithm '{HashAlgorithm}' from provider '{HashAlgorithmProvider}' with HMAC.");
             }
 
             BCryptAlgorithmHandle algorithmHandle = null;
@@ -154,7 +154,7 @@ namespace Microsoft.AspNet.DataProtection.AuthenticatedEncryption
 
             if (logger.IsVerboseLevelEnabled())
             {
-                logger.LogVerbose("Opening CNG algorithm '{0}' from provider '{1}' with chaining mode CBC.", EncryptionAlgorithm, EncryptionAlgorithmProvider);
+                logger.LogVerboseF($"Opening CNG algorithm '{EncryptionAlgorithm}' from provider '{EncryptionAlgorithmProvider}' with chaining mode CBC.");
             }
 
             BCryptAlgorithmHandle algorithmHandle = null;

src/Microsoft.AspNet.DataProtection/AuthenticatedEncryption/CngGcmAuthenticatedEncryptionOptions.cs

@@ -94,7 +94,7 @@ namespace Microsoft.AspNet.DataProtection.AuthenticatedEncryption
 
             if (logger.IsVerboseLevelEnabled())
             {
-                logger.LogVerbose("Opening CNG algorithm '{0}' from provider '{1}' with chaining mode GCM.", EncryptionAlgorithm, EncryptionAlgorithmProvider);
+                logger.LogVerboseF($"Opening CNG algorithm '{EncryptionAlgorithm}' from provider '{EncryptionAlgorithmProvider}' with chaining mode GCM.");
             }
 
             // Special-case cached providers

src/Microsoft.AspNet.DataProtection/AuthenticatedEncryption/ManagedAuthenticatedEncryptionOptions.cs

@@ -88,7 +88,7 @@ namespace Microsoft.AspNet.DataProtection.AuthenticatedEncryption
 
             if (logger.IsVerboseLevelEnabled())
             {
-                logger.LogVerbose("Using managed keyed hash algorithm '{0}'.", ValidationAlgorithmType.FullName);
+                logger.LogVerboseF($"Using managed keyed hash algorithm '{ValidationAlgorithmType.FullName}'.");
             }
 
             if (ValidationAlgorithmType == typeof(HMACSHA256))
@@ -120,7 +120,7 @@ namespace Microsoft.AspNet.DataProtection.AuthenticatedEncryption
 
             if (logger.IsVerboseLevelEnabled())
             {
-                logger.LogVerbose("Using managed symmetric algorithm '{0}'.", EncryptionAlgorithmType.FullName);
+                logger.LogVerboseF($"Using managed symmetric algorithm '{EncryptionAlgorithmType.FullName}'.");
             }
 
             if (EncryptionAlgorithmType == typeof(Aes))

src/Microsoft.AspNet.DataProtection/DataProtectionServices.cs

@@ -43,7 +43,7 @@ namespace Microsoft.Framework.DependencyInjection
                 {
                     if (log.IsInformationLevelEnabled())
                     {
-                        log.LogInformation("Azure Web Sites environment detected. Using '{0}' as key repository; keys will not be encrypted at rest.", azureWebSitesKeysFolder.FullName);
+                        log.LogInformationF($"Azure Web Sites environment detected. Using '{azureWebSitesKeysFolder.FullName}' as key repository; keys will not be encrypted at rest.");
                     }
 
                     // Cloud DPAPI isn't yet available, so we don't encrypt keys at rest.
@@ -68,11 +68,11 @@ namespace Microsoft.Framework.DependencyInjection
                         {
                             if (keyEncryptorDescriptor != null)
                             {
-                                log.LogInformation("User profile is available. Using '{0}' as key repository and Windows DPAPI to encrypt keys at rest.", localAppDataKeysFolder.FullName);
+                                log.LogInformationF($"User profile is available. Using '{localAppDataKeysFolder.FullName}' as key repository and Windows DPAPI to encrypt keys at rest.");
                             }
                             else
                             {
-                                log.LogInformation("User profile is available. Using '{0}' as key repository; keys will not be encrypted at rest.", localAppDataKeysFolder.FullName);
+                                log.LogInformationF($"User profile is available. Using '{localAppDataKeysFolder.FullName}' as key repository; keys will not be encrypted at rest.");
                             }
                         }
                     }
@@ -93,11 +93,11 @@ namespace Microsoft.Framework.DependencyInjection
                             {
                                 if (keyEncryptorDescriptor != null)
                                 {
-                                    log.LogInformation("User profile not available. Using '{0}' as key repository and Windows DPAPI to encrypt keys at rest.", regKeyStorageKey.Name);
+                                    log.LogInformationF($"User profile not available. Using '{regKeyStorageKey.Name}' as key repository and Windows DPAPI to encrypt keys at rest.");
                                 }
                                 else
                                 {
-                                    log.LogInformation("User profile not available. Using '{0}' as key repository; keys will not be encrypted at rest.", regKeyStorageKey.Name);
+                                    log.LogInformationF($"User profile not available. Using '{regKeyStorageKey.Name}' as key repository; keys will not be encrypted at rest.");
                                 }
                             }
                         }

src/Microsoft.AspNet.DataProtection/KeyManagement/DefaultKeyResolver.cs

@@ -62,7 +62,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
             {
                 if (_logger.IsVerboseLevelEnabled())
                 {
-                    _logger.LogVerbose("Considering key '{0:D}' with expiration date {1:u} as default key.", preferredDefaultKey.KeyId, preferredDefaultKey.ExpirationDate);
+                    _logger.LogVerboseF($"Considering key {preferredDefaultKey.KeyId:B} with expiration date {preferredDefaultKey.ExpirationDate:u} as default key.");
                 }
 
                 // if the key has been revoked or is expired, it is no longer a candidate
@@ -70,7 +70,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 {
                     if (_logger.IsVerboseLevelEnabled())
                     {
-                        _logger.LogVerbose("Key '{0:D}' is no longer under consideration as default key because it is expired or revoked.", preferredDefaultKey.KeyId);
+                        _logger.LogVerboseF($"Key {preferredDefaultKey.KeyId:B} is no longer under consideration as default key because it is expired or revoked.");
                     }
                     preferredDefaultKey = null;
                 }

src/Microsoft.AspNet.DataProtection/KeyManagement/KeyRingBasedDataProtector.cs

@@ -63,6 +63,11 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 newPurpose: purpose);
         }
 
+        private static string JoinPurposesForLog(IEnumerable<string> purposes)
+        {
+            return "(" + String.Join(", ", purposes.Select(p => "'" + p + "'")) + ")";
+        }
+
         // allows decrypting payloads whose keys have been revoked
         public byte[] DangerousUnprotect(byte[] protectedData, bool ignoreRevocationErrors, out bool requiresMigration, out bool wasRevoked)
         {
@@ -97,8 +102,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
 
                 if (_logger.IsDebugLevelEnabled())
                 {
-                    _logger.LogDebug("Performing protect operation to key '{0:D}' with purposes ({1}).",
-                        defaultKeyId, String.Join(", ", Purposes.Select(p => "'" + p + "'")));
+                    _logger.LogDebugF($"Performing protect operation to key {defaultKeyId:B} with purposes {JoinPurposesForLog(Purposes)}.");
                 }
 
                 // We'll need to apply the default key id to the template if it hasn't already been applied.
@@ -218,8 +222,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
 
                 if (_logger.IsDebugLevelEnabled())
                 {
-                    _logger.LogDebug("Performing unprotect operation to key '{0:D}' with purposes ({1}).",
-                        keyIdFromPayload, String.Join(", ", Purposes.Select(p => "'" + p + "'")));
+                    _logger.LogDebugF($"Performing unprotect operation to key {keyIdFromPayload:B} with purposes {JoinPurposesForLog(Purposes)}.");
                 }
 
                 // Find the correct encryptor in the keyring.
@@ -228,9 +231,9 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 var requestedEncryptor = currentKeyRing.GetAuthenticatedEncryptorByKeyId(keyIdFromPayload, out keyWasRevoked);
                 if (requestedEncryptor == null)
                 {
-                    if (_logger.IsWarningLevelEnabled())
+                    if (_logger.IsDebugLevelEnabled())
                     {
-                        _logger.LogWarning("Key '{0:D}' was not found in the key ring. Unprotect operation cannot proceed.", keyIdFromPayload);
+                        _logger.LogDebugF($"Key {keyIdFromPayload:B} was not found in the key ring. Unprotect operation cannot proceed.");
                     }
                     throw Error.Common_KeyNotFound(keyIdFromPayload);
                 }
@@ -247,17 +250,17 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 {
                     if (allowOperationsOnRevokedKeys)
                     {
-                        if (_logger.IsWarningLevelEnabled())
+                        if (_logger.IsVerboseLevelEnabled())
                         {
-                            _logger.LogWarning("Key '{0:D}' was revoked. Caller requested unprotect operation proceed regardless.", keyIdFromPayload);
+                            _logger.LogVerboseF($"Key {keyIdFromPayload:B} was revoked. Caller requested unprotect operation proceed regardless.");
                         }
                         status = UnprotectStatus.DecryptionKeyWasRevoked;
                     }
                     else
                     {
-                        if (_logger.IsWarningLevelEnabled())
+                        if (_logger.IsVerboseLevelEnabled())
                         {
-                            _logger.LogWarning("Key '{0:D}' was revoked. Unprotect operation cannot proceed.", keyIdFromPayload);
+                            _logger.LogVerboseF($"Key {keyIdFromPayload:B} was revoked. Unprotect operation cannot proceed.");
                         }
                         throw Error.Common_KeyRevoked(keyIdFromPayload);
                     }

src/Microsoft.AspNet.DataProtection/KeyManagement/KeyRingProvider.cs

@@ -82,7 +82,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 {
                     if (_logger.IsWarningLevelEnabled())
                     {
-                        _logger.LogWarning("Policy resolution states that a new key should be added to the key ring, but automatic generation of keys is disabled. Using fallback key '{0:D}' with expiration {1:u} as default key.", keyToUse.KeyId, keyToUse.ExpirationDate);
+                        _logger.LogWarningF($"Policy resolution states that a new key should be added to the key ring, but automatic generation of keys is disabled. Using fallback key {keyToUse.KeyId:B} with expiration {keyToUse.ExpirationDate:u} as default key.");
                     }
                     return CreateCacheableKeyRingCoreStep2(now, cacheExpirationToken, keyToUse, allKeys);
                 }
@@ -111,7 +111,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
 
             if (_logger.IsVerboseLevelEnabled())
             {
-                _logger.LogVerbose("Using key '{0:D}' as the default key.", defaultKey.KeyId);
+                _logger.LogVerboseF($"Using key {defaultKey.KeyId:B} as the default key.");
             }
 
             DateTimeOffset nextAutoRefreshTime = now + GetRefreshPeriodWithJitter(_keyManagementOptions.KeyRingRefreshPeriod);

src/Microsoft.AspNet.DataProtection/KeyManagement/XmlKeyManager.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Globalization;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.CompilerServices;
@@ -19,6 +18,8 @@ using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
 using Microsoft.Framework.Logging;
 
+using static System.FormattableString;
+
 namespace Microsoft.AspNet.DataProtection.KeyManagement
 {
     /// <summary>
@@ -168,7 +169,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                     // Skip unknown elements.
                     if (_logger.IsWarningLevelEnabled())
                     {
-                        _logger.LogWarning("Unknown element with name '{0}' found in keyring, skipping.", element.Name);
+                        _logger.LogWarningF($"Unknown element with name '{element.Name}' found in keyring, skipping.");
                     }
                 }
             }
@@ -185,14 +186,14 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                         key.SetRevoked();
                         if (_logger.IsVerboseLevelEnabled())
                         {
-                            _logger.LogVerbose("Marked key '{0:D}' as revoked in the keyring.", revokedKeyId);
+                            _logger.LogVerboseF($"Marked key {revokedKeyId:B} as revoked in the keyring.");
                         }
                     }
                     else
                     {
                         if (_logger.IsWarningLevelEnabled())
                         {
-                            _logger.LogWarning("Tried to process revocation of key '{0:D}', but no such key was found in keyring. Skipping.", revokedKeyId);
+                            _logger.LogWarningF($"Tried to process revocation of key {revokedKeyId:B}, but no such key was found in keyring. Skipping.");
                         }
                     }
                 }
@@ -208,7 +209,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                         key.SetRevoked();
                         if (_logger.IsVerboseLevelEnabled())
                         {
-                            _logger.LogVerbose("Marked key '{0:D}' as revoked in the keyring.", key.KeyId);
+                            _logger.LogVerboseF($"Marked key {key.KeyId:B} as revoked in the keyring.");
                         }
                     }
                 }
@@ -247,7 +248,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 // Finally, create the Key instance
                 if (_logger.IsVerboseLevelEnabled())
                 {
-                    _logger.LogVerbose("Found key '{0:D}'.", keyId);
+                    _logger.LogVerboseF($"Found key {keyId:B}.");
                 }
                 return new Key(
                     keyId: keyId,
@@ -264,19 +265,15 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 {
                     if (_logger.IsWarningLevelEnabled())
                     {
-                        _logger.LogWarning("An exception of type '{0}' occurred while processing the key element '{1}', so the key will not be included in the keyring." + Environment.NewLine
-                            + "Full details of the exception will be written to the 'Debug' log.",
-                            ex.GetType().FullName, keyElement.WithoutChildNodes());
+                        _logger.LogWarningF($"An exception of type '{ex.GetType().FullName}' occurred while processing the key element '{keyElement.WithoutChildNodes()}', so the key will not be included in the keyring. Full details of the exception will be written to the 'Debug' log.");
                     }
-                    _logger.LogDebug(ex, "An exception occurred while processing the key element '{0}'.", keyElement);
+                    _logger.LogDebugF(ex, $"An exception occurred while processing the key element '{keyElement}'.");
                 }
                 else
                 {
                     if (_logger.IsWarningLevelEnabled())
                     {
-                        _logger.LogWarning("An exception of type '{0}' occurred while processing the key element '{1}', so the key will not be included in the keyring." + Environment.NewLine
-                            + "To prevent accidental disclosure of sensitive information the full exception details are not being logged. To enable logging full exception details, enable 'Debug' level logging for this provider.",
-                            ex.GetType().FullName, keyElement.WithoutChildNodes());
+                        _logger.LogWarningF($"An exception of type '{ex.GetType().FullName}' occurred while processing the key element '{keyElement.WithoutChildNodes()}', so the key will not be included in the keyring. To prevent accidental disclosure of sensitive information the full exception details are not being logged. To enable logging full exception details, enable 'Debug' level logging for this provider.");
                     }
                 }
 
@@ -299,7 +296,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                     DateTimeOffset massRevocationDate = (DateTimeOffset)revocationElement.Element(RevocationDateElementName);
                     if (_logger.IsVerboseLevelEnabled())
                     {
-                        _logger.LogVerbose("Found revocation of all keys created prior to {0:u}.", massRevocationDate);
+                        _logger.LogVerboseF($"Found revocation of all keys created prior to {massRevocationDate:u}.");
                     }
                     return massRevocationDate;
                 }
@@ -309,7 +306,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                     Guid keyId = XmlConvert.ToGuid(keyIdAsString);
                     if (_logger.IsVerboseLevelEnabled())
                     {
-                        _logger.LogVerbose("Found revocation of key '{0:D}'.", keyId);
+                        _logger.LogVerboseF($"Found revocation of key {keyId:B}.");
                     }
                     return keyId;
                 }
@@ -320,7 +317,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 // revocation information.
                 if (_logger.IsErrorLevelEnabled())
                 {
-                    _logger.LogError(ex, "An exception occurred while processing the revocation element '{0}'. Cannot continue keyring processing.", revocationElement);
+                    _logger.LogErrorF(ex, $"An exception occurred while processing the revocation element '{revocationElement}'. Cannot continue keyring processing.");
                 }
                 throw;
             }
@@ -337,7 +334,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
 
             if (_logger.IsInformationLevelEnabled())
             {
-                _logger.LogInformation("Revoking all keys as of {0:u} for reason '{1}'.", revocationDate, reason);
+                _logger.LogInformationF($"Revoking all keys as of {revocationDate:u} for reason '{reason}'.");
             }
 
             var revocationElement = new XElement(RevocationElementName,
@@ -366,7 +363,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
         {
             if (!suppressLogging && _logger.IsVerboseLevelEnabled())
             {
-                _logger.LogVerbose("Key cache expiration token triggered by '{0}' operation.", opName);
+                _logger.LogVerboseF($"Key cache expiration token triggered by '{opName}' operation.");
             }
 
             Interlocked.Exchange(ref _cacheExpirationTokenSource, new CancellationTokenSource())?.Cancel();
@@ -385,7 +382,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
 
             if (_logger.IsInformationLevelEnabled())
             {
-                _logger.LogInformation("Creating key {0:D} with creation date {1:u}, activation date {2:u}, and expiration date {3:u}.", keyId, creationDate, activationDate, expirationDate);
+                _logger.LogInformationF($"Creating key {keyId:B} with creation date {creationDate:u}, activation date {activationDate:u}, and expiration date {expirationDate:u}.");
             }
 
             var newDescriptor = _authenticatedEncryptorConfiguration.CreateNewDescriptor()
@@ -394,7 +391,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
 
             if (_logger.IsVerboseLevelEnabled())
             {
-                _logger.LogVerbose("Descriptor deserializer type for key {0:D} is {1}.", keyId, descriptorXmlInfo.DeserializerType.AssemblyQualifiedName);
+                _logger.LogVerboseF($"Descriptor deserializer type for key {keyId:B} is '{descriptorXmlInfo.DeserializerType.AssemblyQualifiedName}'.");
             }
 
             // build the <key> element
@@ -413,11 +410,11 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
             {
                 if (_keyEscrowSink != null)
                 {
-                    _logger.LogVerbose("Key escrow sink found. Writing key {0:D} to escrow.", keyId);
+                    _logger.LogVerboseF($"Key escrow sink found. Writing key {keyId:B} to escrow.");
                 }
                 else
                 {
-                    _logger.LogVerbose("No key escrow sink found. Not writing key {0:D} to escrow.", keyId);
+                    _logger.LogVerboseF($"No key escrow sink found. Not writing key {keyId:B} to escrow.");
                 }
             }
             _keyEscrowSink?.Store(keyId, keyElement);
@@ -425,12 +422,12 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
             // If an XML encryptor has been configured, protect secret key material now.
             if (KeyEncryptor == null && _logger.IsWarningLevelEnabled())
             {
-                _logger.LogWarning("No XML encryptor configured. Key {0:D} may be persisted to storage in unencrypted form.", keyId);
+                _logger.LogWarningF($"No XML encryptor configured. Key {keyId:B} may be persisted to storage in unencrypted form.");
             }
             var possiblyEncryptedKeyElement = KeyEncryptor?.EncryptIfNecessary(keyElement) ?? keyElement;
 
             // Persist it to the underlying repository and trigger the cancellation token.
-            string friendlyName = String.Format(CultureInfo.InvariantCulture, "key-{0:D}", keyId);
+            string friendlyName = Invariant($"key-{keyId:D}");
             KeyRepository.StoreElement(possiblyEncryptedKeyElement, friendlyName);
             TriggerAndResetCacheExpirationToken();
 
@@ -453,7 +450,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
 
             if (_logger.IsInformationLevelEnabled())
             {
-                _logger.LogInformation("Revoking key {0:D} at {1:u} for reason '{2}'.", keyId, revocationDate, reason);
+                _logger.LogInformationF($"Revoking key {keyId:B} at {revocationDate:u} for reason '{reason}'.");
             }
 
             var revocationElement = new XElement(RevocationElementName,
@@ -464,7 +461,7 @@ namespace Microsoft.AspNet.DataProtection.KeyManagement
                 new XElement(ReasonElementName, reason));
 
             // Persist it to the underlying repository and trigger the cancellation token
-            string friendlyName = String.Format(CultureInfo.InvariantCulture, "revocation-{0:D}", keyId);
+            string friendlyName = Invariant($"revocation-{keyId:D}");
             KeyRepository.StoreElement(revocationElement, friendlyName);
             TriggerAndResetCacheExpirationToken();
         }

src/Microsoft.AspNet.DataProtection/LoggingExtensions.cs

@@ -8,7 +8,8 @@ using Microsoft.Framework.Logging.Internal;
 namespace Microsoft.Framework.Logging
 {
     /// <summary>
-    /// Helpful extension methods on ILogger.
+    /// Helpful extension methods on <see cref="ILogger"/>.
+    /// Methods ending in *F take <see cref="FormattableString"/> as a parameter.
     /// </summary>
     internal static class LoggingExtensions
     {
@@ -68,19 +69,44 @@ namespace Microsoft.Framework.Logging
             return (logger != null && logger.IsEnabled(level));
         }
 
-        public static void LogDebug(this ILogger logger, Exception error, string message, params object[] args)
+        public static void LogDebugF(this ILogger logger, FormattableString message)
         {
-            logger.LogDebug(new FormattedLogValues(message, args), error);
+            logger.LogDebug(message.Format, message.GetArguments());
         }
 
-        public static void LogError(this ILogger logger, Exception error, string message, params object[] args)
+        public static void LogDebugF(this ILogger logger, Exception error, FormattableString message)
         {
-            logger.LogError(new FormattedLogValues(message, args), error);
+            logger.LogDebug(new FormattedLogValues(message.Format, message.GetArguments()), error);
         }
 
-        public static void LogWarning(this ILogger logger, Exception error, string message, params object[] args)
+        public static void LogError(this ILogger logger, Exception error, string message)
         {
-            logger.LogWarning(new FormattedLogValues(message, args), error);
+            logger.LogError(message, error);
+        }
+
+        public static void LogErrorF(this ILogger logger, Exception error, FormattableString message)
+        {
+            logger.LogError(new FormattedLogValues(message.Format, message.GetArguments()), error);
+        }
+
+        public static void LogInformationF(this ILogger logger, FormattableString message)
+        {
+            logger.LogInformation(message.Format, message.GetArguments());
+        }
+
+        public static void LogVerboseF(this ILogger logger, FormattableString message)
+        {
+            logger.LogVerbose(message.Format, message.GetArguments());
+        }
+
+        public static void LogWarningF(this ILogger logger, FormattableString message)
+        {
+            logger.LogWarning(message.Format, message.GetArguments());
+        }
+
+        public static void LogWarningF(this ILogger logger, Exception error, FormattableString message)
+        {
+            logger.LogWarning(new FormattedLogValues(message.Format, message.GetArguments()), error);
         }
     }
 }

src/Microsoft.AspNet.DataProtection/Properties/Resources.Designer.cs

@@ -107,7 +107,7 @@ namespace Microsoft.AspNet.DataProtection
         }
 
         /// <summary>
-        /// The key '{0:D}' was not found in the key ring.
+        /// The key {0:B} was not found in the key ring.
         /// </summary>
         internal static string Common_KeyNotFound
         {
@@ -115,7 +115,7 @@ namespace Microsoft.AspNet.DataProtection
         }
 
         /// <summary>
-        /// The key '{0:D}' was not found in the key ring.
+        /// The key {0:B} was not found in the key ring.
         /// </summary>
         internal static string FormatCommon_KeyNotFound()
         {
@@ -123,7 +123,7 @@ namespace Microsoft.AspNet.DataProtection
         }
 
         /// <summary>
-        /// The key '{0:D}' has been revoked.
+        /// The key {0:B} has been revoked.
         /// </summary>
         internal static string Common_KeyRevoked
         {
@@ -131,7 +131,7 @@ namespace Microsoft.AspNet.DataProtection
         }
 
         /// <summary>
-        /// The key '{0:D}' has been revoked.
+        /// The key {0:B} has been revoked.
         /// </summary>
         internal static string FormatCommon_KeyRevoked()
         {
@@ -235,7 +235,7 @@ namespace Microsoft.AspNet.DataProtection
         }
 
         /// <summary>
-        /// The key '{0:D}' already exists in the keyring.
+        /// The key {0:B} already exists in the keyring.
         /// </summary>
         internal static string XmlKeyManager_DuplicateKey
         {
@@ -243,7 +243,7 @@ namespace Microsoft.AspNet.DataProtection
         }
 
         /// <summary>
-        /// The key '{0:D}' already exists in the keyring.
+        /// The key {0:B} already exists in the keyring.
         /// </summary>
         internal static string FormatXmlKeyManager_DuplicateKey()
         {

src/Microsoft.AspNet.DataProtection/Repositories/FileSystemXmlRepository.cs

@@ -153,7 +153,7 @@ namespace Microsoft.AspNet.DataProtection.Repositories
         {
             if (_logger.IsVerboseLevelEnabled())
             {
-                _logger.LogVerbose("Reading data from file '{0}'.", fullPath);
+                _logger.LogVerboseF($"Reading data from file '{fullPath}'.");
             }
 
             using (var fileStream = File.OpenRead(fullPath))
@@ -169,7 +169,7 @@ namespace Microsoft.AspNet.DataProtection.Repositories
                 string newFriendlyName = Guid.NewGuid().ToString();
                 if (_logger.IsVerboseLevelEnabled())
                 {
-                    _logger.LogVerbose("The name '{0}' is not a safe file name, using '{1}' instead.", friendlyName, newFriendlyName);
+                    _logger.LogVerboseF($"The name '{friendlyName}' is not a safe file name, using '{newFriendlyName}' instead.");
                 }
                 friendlyName = newFriendlyName;
             }
@@ -198,7 +198,7 @@ namespace Microsoft.AspNet.DataProtection.Repositories
                 // Renames are atomic operations on the file systems we support.
                 if (_logger.IsInformationLevelEnabled())
                 {
-                    _logger.LogInformation("Writing data to file '{0}.", finalFilename);
+                    _logger.LogInformationF($"Writing data to file '{finalFilename}'.");
                 }
                 File.Move(tempFilename, finalFilename);
             }

src/Microsoft.AspNet.DataProtection/Repositories/RegistryXmlRepository.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Globalization;
 using System.Linq;
 using System.Security.Principal;
 using System.Xml.Linq;
@@ -11,6 +10,8 @@ using Microsoft.Framework.Internal;
 using Microsoft.Framework.Logging;
 using Microsoft.Win32;
 
+using static System.FormattableString;
+
 namespace Microsoft.AspNet.DataProtection.Repositories
 {
     /// <summary>
@@ -96,7 +97,7 @@ namespace Microsoft.AspNet.DataProtection.Repositories
                     // Even though this is in HKLM, WAS ensures that applications hosted in IIS are properly isolated.
                     // See APP_POOL::EnsureSharedMachineKeyStorage in WAS source for more info.
                     // The version number will need to change if IIS hosts Core CLR directly.
-                    string aspnetAutoGenKeysBaseKeyName = String.Format(CultureInfo.InvariantCulture, @"SOFTWARE\Microsoft\ASP.NET\4.0.30319.0\AutoGenKeys\{0}", WindowsIdentity.GetCurrent().User.Value);
+                    string aspnetAutoGenKeysBaseKeyName = Invariant($@"SOFTWARE\Microsoft\ASP.NET\4.0.30319.0\AutoGenKeys\{WindowsIdentity.GetCurrent().User.Value}");
                     var aspnetBaseKey = hklmBaseKey.OpenSubKey(aspnetAutoGenKeysBaseKeyName, writable: true);
                     if (aspnetBaseKey != null)
                     {
@@ -132,7 +133,7 @@ namespace Microsoft.AspNet.DataProtection.Repositories
         {
             if (_logger.IsVerboseLevelEnabled())
             {
-                _logger.LogVerbose("Reading data from registry key '{0}', value '{1}'.", regKey.ToString(), valueName);
+                _logger.LogVerboseF($"Reading data from registry key '{regKey}', value '{valueName}'.");
             }
 
             string data = regKey.GetValue(valueName) as string;
@@ -146,7 +147,7 @@ namespace Microsoft.AspNet.DataProtection.Repositories
                 string newFriendlyName = Guid.NewGuid().ToString();
                 if (_logger.IsVerboseLevelEnabled())
                 {
-                    _logger.LogVerbose("The name '{0}' is not a safe registry value name, using '{1}' instead.", friendlyName, newFriendlyName);
+                    _logger.LogVerboseF($"The name '{friendlyName}' is not a safe registry value name, using '{newFriendlyName}' instead.");
                 }
                 friendlyName = newFriendlyName;
             }

src/Microsoft.AspNet.DataProtection/Resources.resx

@@ -136,10 +136,10 @@
     <value>An error occurred while trying to encrypt the provided data. Refer to the inner exception for more information.</value>
   </data>
   <data name="Common_KeyNotFound" xml:space="preserve">
-    <value>The key '{0:D}' was not found in the key ring.</value>
+    <value>The key {0:B} was not found in the key ring.</value>
   </data>
   <data name="Common_KeyRevoked" xml:space="preserve">
-    <value>The key '{0:D}' has been revoked.</value>
+    <value>The key {0:B} has been revoked.</value>
   </data>
   <data name="ProtectionProvider_BadMagicHeader" xml:space="preserve">
     <value>The provided payload cannot be decrypted because it was not protected with this protection provider.</value>
@@ -160,7 +160,7 @@
     <value>The new key lifetime must be at least one week.</value>
   </data>
   <data name="XmlKeyManager_DuplicateKey" xml:space="preserve">
-    <value>The key '{0:D}' already exists in the keyring.</value>
+    <value>The key {0:B} already exists in the keyring.</value>
   </data>
   <data name="Common_ArgumentCannotBeNullOrEmpty" xml:space="preserve">
     <value>Argument cannot be null or empty.</value>

src/Microsoft.AspNet.DataProtection/StringInterpolation.cs

@@ -0,0 +1,43 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+#if !DNXCORE50
+// These classes allow using the C# string interpolation feature from .NET 4.5.1.
+// They're slimmed-down versions of the classes that exist in .NET 4.6.
+
+using System.Globalization;
+
+namespace System
+{
+    internal struct FormattableString
+    {
+        private readonly object[] _arguments;
+        public readonly string Format;
+
+        internal FormattableString(string format, params object[] arguments)
+        {
+            Format = format;
+            _arguments = arguments;
+        }
+
+        public object[] GetArguments() => _arguments;
+
+        public static string Invariant(FormattableString formattable)
+        {
+            return String.Format(CultureInfo.InvariantCulture, formattable.Format, formattable.GetArguments());
+        }
+    }
+}
+
+namespace System.Runtime.CompilerServices
+{
+    internal static class FormattableStringFactory
+    {
+        public static FormattableString Create(string format, params object[] arguments)
+        {
+            return new FormattableString(format, arguments);
+        }
+    }
+}
+
+#endif

src/Microsoft.AspNet.DataProtection/XmlEncryption/CertificateXmlEncryptor.cs

@@ -132,7 +132,7 @@ namespace Microsoft.AspNet.DataProtection.XmlEncryption
                 {
                     if (_logger.IsErrorLevelEnabled())
                     {
-                        _logger.LogError(ex, "An exception occurred while trying to resolve certificate with thumbprint '{0}'.", thumbprint);
+                        _logger.LogErrorF(ex, $"An exception occurred while trying to resolve certificate with thumbprint '{thumbprint}'.");
                     }
                     throw;
                 }
@@ -146,7 +146,7 @@ namespace Microsoft.AspNet.DataProtection.XmlEncryption
 
             if (_logger.IsVerboseLevelEnabled())
             {
-                _logger.LogVerbose("Encrypting to X.509 certificate with thumbprint '{0}'.", cert.Thumbprint);
+                _logger.LogVerboseF($"Encrypting to X.509 certificate with thumbprint '{cert.Thumbprint}'.");
             }
 
             try
@@ -157,7 +157,7 @@ namespace Microsoft.AspNet.DataProtection.XmlEncryption
             {
                 if (_logger.IsErrorLevelEnabled())
                 {
-                    _logger.LogError(ex, "An error occurred while encrypting to X.509 certificate with thumbprint '{0}'.", cert.Thumbprint);
+                    _logger.LogErrorF(ex, $"An error occurred while encrypting to X.509 certificate with thumbprint '{cert.Thumbprint}'.");
                 }
                 throw;
             }

src/Microsoft.AspNet.DataProtection/XmlEncryption/DpapiNGXmlDecryptor.cs

@@ -68,7 +68,7 @@ namespace Microsoft.AspNet.DataProtection.XmlEncryption
                         // swallow all errors - it's just a log
                         protectionDescriptorRule = null;
                     }
-                    _logger.LogVerbose("Decrypting secret element using Windows DPAPI-NG with protection descriptor '{0}'.", protectionDescriptorRule);
+                    _logger.LogVerboseF($"Decrypting secret element using Windows DPAPI-NG with protection descriptor rule '{protectionDescriptorRule}'.");
                 }
 
                 using (Secret secret = DpapiSecretSerializerHelper.UnprotectWithDpapiNG(protectedSecret))

src/Microsoft.AspNet.DataProtection/XmlEncryption/DpapiNGXmlEncryptor.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Globalization;
 using System.Security.Principal;
 using System.Xml.Linq;
 using Microsoft.AspNet.Cryptography;
@@ -11,6 +10,8 @@ using Microsoft.AspNet.DataProtection.Cng;
 using Microsoft.Framework.Internal;
 using Microsoft.Framework.Logging;
 
+using static System.FormattableString;
+
 namespace Microsoft.AspNet.DataProtection.XmlEncryption
 {
     /// <summary>
@@ -65,7 +66,7 @@ namespace Microsoft.AspNet.DataProtection.XmlEncryption
             string protectionDescriptorRuleString = _protectionDescriptorHandle.GetProtectionDescriptorRuleString();
             if (_logger.IsVerboseLevelEnabled())
             {
-                _logger.LogVerbose("Encrypting to Windows DPAPI-NG using protection descriptor '{0}'.", protectionDescriptorRuleString);
+                _logger.LogVerboseF($"Encrypting to Windows DPAPI-NG using protection descriptor rule '{protectionDescriptorRuleString}'.");
             }
 
             // Convert the XML element to a binary secret so that it can be run through DPAPI
@@ -114,7 +115,7 @@ namespace Microsoft.AspNet.DataProtection.XmlEncryption
             using (WindowsIdentity currentIdentity = WindowsIdentity.GetCurrent())
             {
                 // use the SID to create an SDDL string
-                return String.Format(CultureInfo.InvariantCulture, "SID={0}", currentIdentity.User.Value);
+                return Invariant($"SID={currentIdentity.User.Value}");
             }
         }
     }

src/Microsoft.AspNet.DataProtection/XmlEncryption/DpapiXmlEncryptor.cs

@@ -66,7 +66,7 @@ namespace Microsoft.AspNet.DataProtection.XmlEncryption
                 }
                 else
                 {
-                    _logger.LogVerbose("Encrypting to Windows DPAPI for current user account ({0}).", WindowsIdentity.GetCurrent().Name);
+                    _logger.LogVerboseF($"Encrypting to Windows DPAPI for current user account ({WindowsIdentity.GetCurrent().Name}).");
                 }
             }