Right-size Lists when created (#23714)

martincostello · web-flow · commit b22512de0e5d · 2020-08-19T09:45:52.000-07:00
Create new instances of List&lt;T&gt; with an appropriate capacity for the items that will be added.
Use Array.Empty&lt;T&gt;() where appropriate, rather than create an empty list and then return it.
diff --git a/src/FileProviders/Embedded/src/Manifest/ManifestDirectory.cs b/src/FileProviders/Embedded/src/Manifest/ManifestDirectory.cs
@@ -98,7 +98,7 @@ internal static void ValidateChildrenAndSetParent(ManifestEntry[] children, Mani
 
         private ManifestEntry[] CopyChildren()
         {
-            var list = new List<ManifestEntry>();
+            var list = new List<ManifestEntry>(Children.Count);
             for (int i = 0; i < Children.Count; i++)
             {
                 var child = Children[i];
diff --git a/src/Http/Http/src/Features/RequestCookiesFeature.cs b/src/Http/Http/src/Features/RequestCookiesFeature.cs
@@ -80,7 +80,7 @@ public IRequestCookieCollection Cookies
                     }
                     else
                     {
-                        var headers = new List<string>();
+                        var headers = new List<string>(_parsedValues.Count);
                         foreach (var pair in _parsedValues)
                         {
                             headers.Add(new CookieHeaderValue(pair.Key, pair.Value).ToString());
diff --git a/src/Http/Routing/src/Patterns/RoutePatternFactory.cs b/src/Http/Routing/src/Patterns/RoutePatternFactory.cs
@@ -497,7 +497,7 @@ RoutePatternPart VisitPart(RoutePatternPart part)
                         updatedParameterPolicies = new Dictionary<string, List<RoutePatternParameterPolicyReference>>(StringComparer.OrdinalIgnoreCase);
                     }
 
-                    parameterConstraints = new List<RoutePatternParameterPolicyReference>();
+                    parameterConstraints = new List<RoutePatternParameterPolicyReference>(parameter.ParameterPolicies.Count);
                     updatedParameterPolicies.Add(parameter.Name, parameterConstraints);
                 }
 
diff --git a/src/Identity/Core/src/SignInManager.cs b/src/Identity/Core/src/SignInManager.cs
@@ -169,16 +169,22 @@ public virtual async Task<bool> CanSignInAsync(TUser user)
         public virtual async Task RefreshSignInAsync(TUser user)
         {
             var auth = await Context.AuthenticateAsync(IdentityConstants.ApplicationScheme);
-            var claims = new List<Claim>();
+            IList<Claim> claims = Array.Empty<Claim>();
+
             var authenticationMethod = auth?.Principal?.FindFirst(ClaimTypes.AuthenticationMethod);
-            if (authenticationMethod != null)
-            {
-                claims.Add(authenticationMethod);
-            }
             var amr = auth?.Principal?.FindFirst("amr");
-            if (amr != null)
+
+            if (authenticationMethod != null || amr != null)
             {
-                claims.Add(amr);
+                claims = new List<Claim>();
+                if (authenticationMethod != null)
+                {
+                    claims.Add(authenticationMethod);
+                }
+                if (amr != null)
+                {
+                    claims.Add(amr);
+                }
             }
 
             await SignInWithClaimsAsync(user, auth?.Properties, claims);
@@ -203,9 +209,10 @@ public virtual Task SignInAsync(TUser user, bool isPersistent, string authentica
         /// <returns>The task object representing the asynchronous operation.</returns>
         public virtual Task SignInAsync(TUser user, AuthenticationProperties authenticationProperties, string authenticationMethod = null)
         {
-            var additionalClaims = new List<Claim>();
+            IList<Claim> additionalClaims = Array.Empty<Claim>();
             if (authenticationMethod != null)
             {
+                additionalClaims = new List<Claim>();
                 additionalClaims.Add(new Claim(ClaimTypes.AuthenticationMethod, authenticationMethod));
             }
             return SignInWithClaimsAsync(user, authenticationProperties, additionalClaims);
diff --git a/src/Middleware/Localization/src/RequestLocalizationOptions.cs b/src/Middleware/Localization/src/RequestLocalizationOptions.cs
@@ -122,7 +122,7 @@ public RequestCulture DefaultRequestCulture
         /// <returns>The <see cref="RequestLocalizationOptions"/>.</returns>
         public RequestLocalizationOptions AddSupportedCultures(params string[] cultures)
         {
-            var supportedCultures = new List<CultureInfo>();
+            var supportedCultures = new List<CultureInfo>(cultures.Length);
 
             foreach (var culture in cultures)
             {
@@ -140,7 +140,7 @@ public RequestLocalizationOptions AddSupportedCultures(params string[] cultures)
         /// <returns>The <see cref="RequestLocalizationOptions"/>.</returns>
         public RequestLocalizationOptions AddSupportedUICultures(params string[] uiCultures)
         {
-            var supportedUICultures = new List<CultureInfo>();
+            var supportedUICultures = new List<CultureInfo>(uiCultures.Length);
             foreach (var culture in uiCultures)
             {
                 supportedUICultures.Add(new CultureInfo(culture));
diff --git a/src/Mvc/Mvc.Core/src/ApplicationModels/ApplicationModelFactory.cs b/src/Mvc/Mvc.Core/src/ApplicationModels/ApplicationModelFactory.cs
@@ -309,7 +309,7 @@ private static string CreateMixedRoutedActionDescriptorsErrorMessage(
             // Text to show as the attribute route template for conventionally routed actions.
             var nullTemplate = Resources.AttributeRoute_NullTemplateRepresentation;
 
-            var actionDescriptions = new List<string>();
+            var actionDescriptions = new List<string>(actions.Count);
             for (var i = 0; i < actions.Count; i++)
             {
                 var (action, selector) = actions[i];
diff --git a/src/Mvc/Mvc.Core/src/ApplicationModels/ControllerActionDescriptorBuilder.cs b/src/Mvc/Mvc.Core/src/ApplicationModels/ControllerActionDescriptorBuilder.cs
@@ -63,7 +63,7 @@ private static void AddControllerPropertyDescriptors(ActionDescriptor actionDesc
 
         private static void AddParameterDescriptors(ActionDescriptor actionDescriptor, ActionModel action)
         {
-            var parameterDescriptors = new List<ParameterDescriptor>();
+            var parameterDescriptors = new List<ParameterDescriptor>(action.Parameters.Count);
             foreach (var parameter in action.Parameters)
             {
                 var parameterDescriptor = CreateParameterDescriptor(parameter);
diff --git a/src/Mvc/Mvc.Core/src/ApplicationModels/DefaultApplicationModelProvider.cs b/src/Mvc/Mvc.Core/src/ApplicationModels/DefaultApplicationModelProvider.cs
@@ -352,7 +352,7 @@ internal ActionModel CreateActionModel(
 
             // This is fairly complicated so that we maintain referential equality between items in
             // ActionModel.Attributes and ActionModel.Attributes[*].Attribute.
-            var applicableAttributes = new List<object>();
+            var applicableAttributes = new List<object>(routeAttributes.Length);
             foreach (var attribute in attributes)
             {
                 if (attribute is IRouteTemplateProvider)
diff --git a/src/Mvc/Mvc.Core/src/BindAttribute.cs b/src/Mvc/Mvc.Core/src/BindAttribute.cs
@@ -25,7 +25,7 @@ public class BindAttribute : Attribute, IModelNameProvider, IPropertyFilterProvi
         /// <param name="include">Names of parameters to include in binding.</param>
         public BindAttribute(params string[] include)
         {
-            var items = new List<string>();
+            var items = new List<string>(include.Length);
             foreach (var item in include)
             {
                 items.AddRange(SplitString(item));
diff --git a/src/Mvc/Mvc.Core/src/ConsumesAttribute.cs b/src/Mvc/Mvc.Core/src/ConsumesAttribute.cs
@@ -199,7 +199,7 @@ private bool IsApplicable(ActionDescriptor actionDescriptor)
 
         private MediaTypeCollection GetContentTypes(string firstArg, string[] args)
         {
-            var completeArgs = new List<string>();
+            var completeArgs = new List<string>(args.Length + 1);
             completeArgs.Add(firstArg);
             completeArgs.AddRange(args);
             var contentTypes = new MediaTypeCollection();
diff --git a/src/Mvc/Mvc.Core/src/Formatters/InputFormatter.cs b/src/Mvc/Mvc.Core/src/Formatters/InputFormatter.cs
@@ -159,7 +159,7 @@ public virtual IReadOnlyList<string> GetSupportedContentTypes(string contentType
                     {
                         if (mediaTypes == null)
                         {
-                            mediaTypes = new List<string>();
+                            mediaTypes = new List<string>(SupportedMediaTypes.Count);
                         }
 
                         mediaTypes.Add(mediaType);
diff --git a/src/Mvc/Mvc.Core/src/Formatters/OutputFormatter.cs b/src/Mvc/Mvc.Core/src/Formatters/OutputFormatter.cs
@@ -67,7 +67,7 @@ public virtual IReadOnlyList<string> GetSupportedContentTypes(
                     {
                         if (mediaTypes == null)
                         {
-                            mediaTypes = new List<string>();
+                            mediaTypes = new List<string>(SupportedMediaTypes.Count);
                         }
 
                         mediaTypes.Add(contentType);
@@ -81,7 +81,7 @@ public virtual IReadOnlyList<string> GetSupportedContentTypes(
                     {
                         if (mediaTypes == null)
                         {
-                            mediaTypes = new List<string>();
+                            mediaTypes = new List<string>(SupportedMediaTypes.Count);
                         }
 
                         mediaTypes.Add(mediaType);
diff --git a/src/Mvc/Mvc.Core/src/Infrastructure/ActionSelector.cs b/src/Mvc/Mvc.Core/src/Infrastructure/ActionSelector.cs
@@ -135,10 +135,11 @@ private IReadOnlyList<ActionDescriptor> EvaluateActionConstraints(
             RouteContext context,
             IReadOnlyList<ActionDescriptor> actions)
         {
-            var candidates = new List<ActionSelectorCandidate>();
+            var actionsCount = actions.Count;
+            var candidates = new List<ActionSelectorCandidate>(actionsCount);
 
             // Perf: Avoid allocations
-            for (var i = 0; i < actions.Count; i++)
+            for (var i = 0; i < actionsCount; i++)
             {
                 var action = actions[i];
                 var constraints = _actionConstraintCache.GetActionConstraints(context.HttpContext, action);
@@ -150,9 +151,10 @@ private IReadOnlyList<ActionDescriptor> EvaluateActionConstraints(
             List<ActionDescriptor> results = null;
             if (matches != null)
             {
-                results = new List<ActionDescriptor>(matches.Count);
+                var matchesCount = matches.Count;
+                results = new List<ActionDescriptor>(matchesCount);
                 // Perf: Avoid allocations
-                for (var i = 0; i < matches.Count; i++)
+                for (var i = 0; i < matchesCount; i++)
                 {
                     var candidate = matches[i];
                     results.Add(candidate.Action);
diff --git a/src/Mvc/Mvc.Core/src/ProducesAttribute.cs b/src/Mvc/Mvc.Core/src/ProducesAttribute.cs
@@ -111,7 +111,7 @@ public void SetContentTypes(MediaTypeCollection contentTypes)
 
         private MediaTypeCollection GetContentTypes(string firstArg, string[] args)
         {
-            var completeArgs = new List<string>();
+            var completeArgs = new List<string>(args.Length + 1);
             completeArgs.Add(firstArg);
             completeArgs.AddRange(args);
             var contentTypes = new MediaTypeCollection();
diff --git a/src/Mvc/Mvc.Razor.RuntimeCompilation/src/RazorReferenceManager.cs b/src/Mvc/Mvc.Razor.RuntimeCompilation/src/RazorReferenceManager.cs
@@ -52,7 +52,7 @@ private IReadOnlyList<MetadataReference> GetCompilationReferences()
         // For unit testing
         internal IEnumerable<string> GetReferencePaths()
         {
-            var referencePaths = new List<string>();
+            var referencePaths = new List<string>(_options.AdditionalReferencePaths.Count);
 
             foreach (var part in _partManager.ApplicationParts)
             {
diff --git a/src/Mvc/Mvc.ViewFeatures/src/Infrastructure/DefaultTempDataSerializer.cs b/src/Mvc/Mvc.ViewFeatures/src/Infrastructure/DefaultTempDataSerializer.cs
@@ -83,7 +83,8 @@ private IDictionary<string, object> DeserializeDictionary(JsonElement rootElemen
 
         private static object DeserializeArray(in JsonElement arrayElement)
         {
-            if (arrayElement.GetArrayLength() == 0)
+            int arrayLength = arrayElement.GetArrayLength();
+            if (arrayLength == 0)
             {
                 // We have to infer the type of the array by inspecting it's elements.
                 // If there's nothing to inspect, return a null value since we do not know
@@ -93,7 +94,7 @@ private static object DeserializeArray(in JsonElement arrayElement)
 
             if (arrayElement[0].ValueKind == JsonValueKind.String)
             {
-                var array = new List<string>();
+                var array = new List<string>(arrayLength);
 
                 foreach (var item in arrayElement.EnumerateArray())
                 {
@@ -104,7 +105,7 @@ private static object DeserializeArray(in JsonElement arrayElement)
             }
             else if (arrayElement[0].ValueKind == JsonValueKind.Number)
             {
-                var array = new List<int>();
+                var array = new List<int>(arrayLength);
 
                 foreach (var item in arrayElement.EnumerateArray())
                 {
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentEventHandlerLoweringPass.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentEventHandlerLoweringPass.cs
@@ -170,7 +170,7 @@ private IntermediateNode RewriteUsage(IntermediateNode parent, TagHelperDirectiv
             // This method is overloaded on string and T, which means that it will put the code in the
             // correct context for intellisense when typing in the attribute.
             var eventArgsType = node.TagHelper.GetEventArgsType();
-            var tokens = new List<IntermediateToken>()
+            var tokens = new List<IntermediateToken>(original.Count + 2)
             {
                 new IntermediateToken()
                 {
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Tools/src/Application.cs b/src/Razor/Microsoft.AspNetCore.Razor.Tools/src/Application.cs
@@ -96,7 +96,7 @@ private string GetInformationalVersion()
 
         private static string[] ExpandResponseFiles(string[] args)
         {
-            var expandedArgs = new List<string>();
+            var expandedArgs = new List<string>(args.Length);
             foreach (var arg in args)
             {
                 if (!arg.StartsWith("@", StringComparison.Ordinal))
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Tools/src/DefaultRequestDispatcher.cs b/src/Razor/Microsoft.AspNetCore.Razor.Tools/src/DefaultRequestDispatcher.cs
@@ -143,7 +143,7 @@ private void HandleCancellation()
         /// </summary>
         private void WaitForAnyCompletion(CancellationToken cancellationToken)
         {
-            var all = new List<Task>();
+            var all = new List<Task>(_connections.Count + 3);
             all.AddRange(_connections);
             all.Add(_timeoutTask);
             all.Add(_listenTask);
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Tools/src/MetadataReaderExtensions.cs b/src/Razor/Microsoft.AspNetCore.Razor.Tools/src/MetadataReaderExtensions.cs
@@ -33,7 +33,7 @@ internal static AssemblyIdentity GetAssemblyIdentity(this MetadataReader reader)
         
         internal static AssemblyIdentity[] GetReferencedAssembliesOrThrow(this MetadataReader reader)
         {
-            var references = new List<AssemblyIdentity>();
+            var references = new List<AssemblyIdentity>(reader.AssemblyReferences.Count);
 
             foreach (var referenceHandle in reader.AssemblyReferences)
             {
diff --git a/src/Razor/Microsoft.NET.Sdk.Razor/src/FindAssembliesWithReferencesTo.cs b/src/Razor/Microsoft.NET.Sdk.Razor/src/FindAssembliesWithReferencesTo.cs
@@ -23,7 +23,7 @@ public class FindAssembliesWithReferencesTo : Task
 
         public override bool Execute()
         {
-            var referenceItems = new List<AssemblyItem>();
+            var referenceItems = new List<AssemblyItem>(Assemblies.Length);
             foreach (var item in Assemblies)
             {
                 const string FusionNameKey = "FusionName";
diff --git a/src/Razor/Microsoft.NET.Sdk.Razor/src/ReferenceResolver.cs b/src/Razor/Microsoft.NET.Sdk.Razor/src/ReferenceResolver.cs
@@ -120,7 +120,7 @@ protected virtual IReadOnlyList<AssemblyItem> GetReferences(string file)
 
                 var metadataReader = peReader.GetMetadataReader();
 
-                var references = new List<AssemblyItem>();
+                var references = new List<AssemblyItem>(metadataReader.AssemblyReferences.Count);
                 foreach (var handle in metadataReader.AssemblyReferences)
                 {
                     var reference = metadataReader.GetAssemblyReference(handle);
diff --git a/src/Razor/Razor/src/TagHelpers/ReadOnlyTagHelperAttributeList.cs b/src/Razor/Razor/src/TagHelpers/ReadOnlyTagHelperAttributeList.cs
@@ -12,8 +12,6 @@ namespace Microsoft.AspNetCore.Razor.TagHelpers
     /// </summary>
     public abstract class ReadOnlyTagHelperAttributeList : ReadOnlyCollection<TagHelperAttribute>
     {
-        private static readonly IReadOnlyList<TagHelperAttribute> EmptyList = new TagHelperAttribute[0];
-
         /// <summary>
         /// Instantiates a new instance of <see cref="ReadOnlyTagHelperAttributeList"/> with an empty
         /// collection.
@@ -146,7 +144,7 @@ public bool TryGetAttributes(string name, out IReadOnlyList<TagHelperAttribute>
                     matchedAttributes.Add(attribute);
                 }
             }
-            attributes = matchedAttributes ?? EmptyList;
+            attributes = matchedAttributes ?? (IReadOnlyList<TagHelperAttribute>)Array.Empty<TagHelperAttribute>();
 
             return matchedAttributes != null;
         }
@@ -198,4 +196,4 @@ protected static bool NameEquals(string name, TagHelperAttribute attribute)
             return string.Equals(name, attribute.Name, StringComparison.OrdinalIgnoreCase);
         }
     }
-}
+}
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.MvcShim/Microsoft.AspNetCore.Razor.TagHelpers/ReadOnlyTagHelperAttributeList.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.MvcShim/Microsoft.AspNetCore.Razor.TagHelpers/ReadOnlyTagHelperAttributeList.cs
@@ -12,8 +12,6 @@ namespace Microsoft.AspNetCore.Razor.TagHelpers
     /// </summary>
     public abstract class ReadOnlyTagHelperAttributeList : ReadOnlyCollection<TagHelperAttribute>
     {
-        private static readonly IReadOnlyList<TagHelperAttribute> EmptyList = new TagHelperAttribute[0];
-
         /// <summary>
         /// Instantiates a new instance of <see cref="ReadOnlyTagHelperAttributeList"/> with an empty
         /// collection.
@@ -138,7 +136,7 @@ public bool TryGetAttributes(string name, out IReadOnlyList<TagHelperAttribute>
                     matchedAttributes.Add(Items[i]);
                 }
             }
-            attributes = matchedAttributes ?? EmptyList;
+            attributes = matchedAttributes ?? Array.Empty<TagHelperAttribute>() as IReadOnlyList<TagHelperAttribute>;
 
             return matchedAttributes != null;
         }
diff --git a/src/Security/Authentication/Certificate/src/CertificateAuthenticationHandler.cs b/src/Security/Authentication/Certificate/src/CertificateAuthenticationHandler.cs
@@ -131,7 +131,7 @@ private async Task<AuthenticateResult> ValidateCertificateAsync(X509Certificate2
             var certificateIsValid = chain.Build(clientCertificate);
             if (!certificateIsValid)
             {
-                var chainErrors = new List<string>();
+                var chainErrors = new List<string>(chain.ChainStatus.Length);
                 foreach (var validationFailure in chain.ChainStatus)
                 {
                     chainErrors.Add($"{validationFailure.Status} {validationFailure.StatusInformation}");
diff --git a/src/Security/Authentication/JwtBearer/src/JwtBearerHandler.cs b/src/Security/Authentication/JwtBearer/src/JwtBearerHandler.cs
@@ -274,7 +274,7 @@ protected override Task HandleForbiddenAsync(AuthenticationProperties properties
         
         private static string CreateErrorDescription(Exception authFailure)
         {
-            IEnumerable<Exception> exceptions;
+            IReadOnlyCollection<Exception> exceptions;
             if (authFailure is AggregateException agEx)
             {
                 exceptions = agEx.InnerExceptions;
@@ -284,7 +284,7 @@ private static string CreateErrorDescription(Exception authFailure)
                 exceptions = new[] { authFailure };
             }
 
-            var messages = new List<string>();
+            var messages = new List<string>(exceptions.Count);
 
             foreach (var ex in exceptions)
             {
diff --git a/src/Servers/HttpSys/src/AuthenticationManager.cs b/src/Servers/HttpSys/src/AuthenticationManager.cs
@@ -107,13 +107,13 @@ private unsafe void SetUrlGroupSecurity()
 
         internal static IList<string> GenerateChallenges(AuthenticationSchemes authSchemes)
         {
-            IList<string> challenges = new List<string>();
-
             if (authSchemes == AuthenticationSchemes.None)
             {
-                return challenges;
+                return Array.Empty<string>();
             }
 
+            IList<string> challenges = new List<string>();
+
             // Order by strength.
             if ((authSchemes & AuthenticationSchemes.Kerberos) == AuthenticationSchemes.Kerberos)
             {
diff --git a/src/Servers/HttpSys/src/HttpSysListener.cs b/src/Servers/HttpSys/src/HttpSysListener.cs
@@ -343,7 +343,7 @@ internal unsafe void SendError(ulong requestId, int httpStatusCode, IList<string
                 // Copied from the multi-value headers section of SerializeHeaders
                 if (authChallenges != null && authChallenges.Count > 0)
                 {
-                    pinnedHeaders = new List<GCHandle>();
+                    pinnedHeaders = new List<GCHandle>(authChallenges.Count + 3);
 
                     HttpApiTypes.HTTP_RESPONSE_INFO[] knownHeaderInfo = null;
                     knownHeaderInfo = new HttpApiTypes.HTTP_RESPONSE_INFO[1];
diff --git a/src/Shared/Buffers.Testing/ReadOnlySequenceFactory.cs b/src/Shared/Buffers.Testing/ReadOnlySequenceFactory.cs
@@ -92,7 +92,7 @@ public override ReadOnlySequence<byte> CreateOfSize(int size)
 
             public override ReadOnlySequence<byte> CreateWithContent(byte[] data)
             {
-                var segments = new List<byte[]>();
+                var segments = new List<byte[]>((data.Length * 2) + 1);
 
                 segments.Add(Array.Empty<byte>());
                 foreach (var b in data)
diff --git a/src/Shared/ObjectMethodExecutor/ObjectMethodExecutor.cs b/src/Shared/ObjectMethodExecutor/ObjectMethodExecutor.cs
diff --git a/src/Shared/StackTrace/StackFrame/StackTraceHelper.cs b/src/Shared/StackTrace/StackFrame/StackTraceHelper.cs
diff --git a/src/SignalR/common/Http.Connections/src/Internal/HttpConnectionManager.cs b/src/SignalR/common/Http.Connections/src/Internal/HttpConnectionManager.cs
diff --git a/src/SignalR/server/Core/src/HubConnectionHandler.cs b/src/SignalR/server/Core/src/HubConnectionHandler.cs
diff --git a/src/SignalR/server/Core/src/HubOptionsSetup.cs b/src/SignalR/server/Core/src/HubOptionsSetup.cs
diff --git a/src/SignalR/server/StackExchangeRedis/src/Internal/DefaultHubMessageSerializer.cs b/src/SignalR/server/StackExchangeRedis/src/Internal/DefaultHubMessageSerializer.cs
diff --git a/src/SignalR/server/StackExchangeRedis/src/RedisHubLifetimeManager.cs b/src/SignalR/server/StackExchangeRedis/src/RedisHubLifetimeManager.cs

Original file line number	Diff line number	Diff line change
`@@ -98,7 +98,7 @@ internal static void ValidateChildrenAndSetParent(ManifestEntry[] children, Mani`
`98`	`98`
`99`	`99`	`private ManifestEntry[] CopyChildren()`
`100`	`100`	`{`
`101`		`- var list = new List<ManifestEntry>();`
	`101`	`+ var list = new List<ManifestEntry>(Children.Count);`
`102`	`102`	`for (int i = 0; i < Children.Count; i++)`
`103`	`103`	`{`
`104`	`104`	`var child = Children[i];`
Original file line number	Diff line number	Diff line change
`@@ -80,7 +80,7 @@ public IRequestCookieCollection Cookies`
`80`	`80`	`}`
`81`	`81`	`else`
`82`	`82`	`{`
`83`		`- var headers = new List<string>();`
	`83`	`+ var headers = new List<string>(_parsedValues.Count);`
`84`	`84`	`foreach (var pair in _parsedValues)`
`85`	`85`	`{`
`86`	`86`	`headers.Add(new CookieHeaderValue(pair.Key, pair.Value).ToString());`
Original file line number	Diff line number	Diff line change
`@@ -497,7 +497,7 @@ RoutePatternPart VisitPart(RoutePatternPart part)`
`497`	`497`	`updatedParameterPolicies = new Dictionary<string, List<RoutePatternParameterPolicyReference>>(StringComparer.OrdinalIgnoreCase);`
`498`	`498`	`}`
`499`	`499`
`500`		`- parameterConstraints = new List<RoutePatternParameterPolicyReference>();`
	`500`	`+ parameterConstraints = new List<RoutePatternParameterPolicyReference>(parameter.ParameterPolicies.Count);`
`501`	`501`	`updatedParameterPolicies.Add(parameter.Name, parameterConstraints);`
`502`	`502`	`}`
`503`	`503`
Original file line number	Diff line number	Diff line change
`@@ -122,7 +122,7 @@ public RequestCulture DefaultRequestCulture`
`122`	`122`	`/// <returns>The <see cref="RequestLocalizationOptions"/>.</returns>`
`123`	`123`	`public RequestLocalizationOptions AddSupportedCultures(params string[] cultures)`
`124`	`124`	`{`
`125`		`- var supportedCultures = new List<CultureInfo>();`
	`125`	`+ var supportedCultures = new List<CultureInfo>(cultures.Length);`
`126`	`126`
`127`	`127`	`foreach (var culture in cultures)`
`128`	`128`	`{`
`@@ -140,7 +140,7 @@ public RequestLocalizationOptions AddSupportedCultures(params string[] cultures)`
`140`	`140`	`/// <returns>The <see cref="RequestLocalizationOptions"/>.</returns>`
`141`	`141`	`public RequestLocalizationOptions AddSupportedUICultures(params string[] uiCultures)`
`142`	`142`	`{`
`143`		`- var supportedUICultures = new List<CultureInfo>();`
	`143`	`+ var supportedUICultures = new List<CultureInfo>(uiCultures.Length);`
`144`	`144`	`foreach (var culture in uiCultures)`
`145`	`145`	`{`
`146`	`146`	`supportedUICultures.Add(new CultureInfo(culture));`
Original file line number	Diff line number	Diff line change
`@@ -309,7 +309,7 @@ private static string CreateMixedRoutedActionDescriptorsErrorMessage(`
`309`	`309`	`// Text to show as the attribute route template for conventionally routed actions.`
`310`	`310`	`var nullTemplate = Resources.AttributeRoute_NullTemplateRepresentation;`
`311`	`311`
`312`		`- var actionDescriptions = new List<string>();`
	`312`	`+ var actionDescriptions = new List<string>(actions.Count);`
`313`	`313`	`for (var i = 0; i < actions.Count; i++)`
`314`	`314`	`{`
`315`	`315`	`var (action, selector) = actions[i];`
Original file line number	Diff line number	Diff line change
`@@ -63,7 +63,7 @@ private static void AddControllerPropertyDescriptors(ActionDescriptor actionDesc`
`63`	`63`
`64`	`64`	`private static void AddParameterDescriptors(ActionDescriptor actionDescriptor, ActionModel action)`
`65`	`65`	`{`
`66`		`- var parameterDescriptors = new List<ParameterDescriptor>();`
	`66`	`+ var parameterDescriptors = new List<ParameterDescriptor>(action.Parameters.Count);`
`67`	`67`	`foreach (var parameter in action.Parameters)`
`68`	`68`	`{`
`69`	`69`	`var parameterDescriptor = CreateParameterDescriptor(parameter);`
Original file line number	Diff line number	Diff line change
`@@ -352,7 +352,7 @@ internal ActionModel CreateActionModel(`
`352`	`352`
`353`	`353`	`// This is fairly complicated so that we maintain referential equality between items in`
`354`	`354`	`// ActionModel.Attributes and ActionModel.Attributes[*].Attribute.`
`355`		`- var applicableAttributes = new List<object>();`
	`355`	`+ var applicableAttributes = new List<object>(routeAttributes.Length);`
`356`	`356`	`foreach (var attribute in attributes)`
`357`	`357`	`{`
`358`	`358`	`if (attribute is IRouteTemplateProvider)`
Original file line number	Diff line number	Diff line change
`@@ -25,7 +25,7 @@ public class BindAttribute : Attribute, IModelNameProvider, IPropertyFilterProvi`
`25`	`25`	`/// <param name="include">Names of parameters to include in binding.</param>`
`26`	`26`	`public BindAttribute(params string[] include)`
`27`	`27`	`{`
`28`		`- var items = new List<string>();`
	`28`	`+ var items = new List<string>(include.Length);`
`29`	`29`	`foreach (var item in include)`
`30`	`30`	`{`
`31`	`31`	`items.AddRange(SplitString(item));`
Original file line number	Diff line number	Diff line change
`@@ -199,7 +199,7 @@ private bool IsApplicable(ActionDescriptor actionDescriptor)`
`199`	`199`
`200`	`200`	`private MediaTypeCollection GetContentTypes(string firstArg, string[] args)`
`201`	`201`	`{`
`202`		`- var completeArgs = new List<string>();`
	`202`	`+ var completeArgs = new List<string>(args.Length + 1);`
`203`	`203`	`completeArgs.Add(firstArg);`
`204`	`204`	`completeArgs.AddRange(args);`
`205`	`205`	`var contentTypes = new MediaTypeCollection();`