Make structs readonly

src/Microsoft.AspNetCore.Mvc.Abstractions/ActionConstraints/ActionSelectorCandidate.cs

@@ -10,7 +10,7 @@ namespace Microsoft.AspNetCore.Mvc.ActionConstraints
     /// <summary>
     /// A candidate action for action selection.
     /// </summary>
-    public struct ActionSelectorCandidate
+    public readonly struct ActionSelectorCandidate
     {
         /// <summary>
         /// Creates a new <see cref="ActionSelectorCandidate"/>.

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/EnumGroupAndName.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// <summary>
     /// An abstraction used when grouping enum values for <see cref="ModelMetadata.EnumGroupedDisplayNamesAndValues"/>.
     /// </summary>
-    public struct EnumGroupAndName
+    public readonly struct EnumGroupAndName
     {
         private readonly Func<string> _name;
 

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/Metadata/ModelMetadataIdentity.cs

@@ -11,8 +11,20 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
     /// <summary>
     /// A key type which identifies a <see cref="ModelMetadata"/>.
     /// </summary>
-    public struct ModelMetadataIdentity : IEquatable<ModelMetadataIdentity>
+    public readonly struct ModelMetadataIdentity : IEquatable<ModelMetadataIdentity>
     {
+        private ModelMetadataIdentity(
+            Type modelType,
+            string name = null,
+            Type containerType = null,
+            ParameterInfo parameterInfo = null)
+        {
+            ModelType = modelType;
+            Name = name;
+            ContainerType = containerType;
+            ParameterInfo = parameterInfo;
+        }
+
         /// <summary>
         /// Creates a <see cref="ModelMetadataIdentity"/> for the provided model <see cref="Type"/>.
         /// </summary>
@@ -25,10 +37,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
                 throw new ArgumentNullException(nameof(modelType));
             }
 
-            return new ModelMetadataIdentity()
+            return new ModelMetadataIdentity(modelType);
-            {
-                ModelType = modelType,
-            };
         }
 
         /// <summary>
@@ -58,12 +67,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
                 throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(name));
             }
 
-            return new ModelMetadataIdentity()
+            return new ModelMetadataIdentity(modelType, name, containerType);
-            {
-                ModelType = modelType,
-                Name = name,
-                ContainerType = containerType,
-            };
         }
 
         /// <summary>
@@ -93,24 +97,19 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
                 throw new ArgumentNullException(nameof(modelType));
             }
 
-            return new ModelMetadataIdentity()
+            return new ModelMetadataIdentity(modelType, parameter.Name, parameterInfo: parameter);
-            {
-                Name = parameter.Name,
-                ModelType = modelType,
-                ParameterInfo = parameter,
-            };
         }
 
         /// <summary>
         /// Gets the <see cref="Type"/> defining the model property represented by the current
         /// instance, or <c>null</c> if the current instance does not represent a property.
         /// </summary>
-        public Type ContainerType { get; private set; }
+        public Type ContainerType { get; }
 
         /// <summary>
         /// Gets the <see cref="Type"/> represented by the current instance.
         /// </summary>
-        public Type ModelType { get; private set; }
+        public Type ModelType { get; }
 
         /// <summary>
         /// Gets a value indicating the kind of metadata represented by the current instance.
@@ -138,13 +137,13 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
         /// Gets the name of the current instance if it represents a parameter or property, or <c>null</c> if
         /// the current instance represents a type.
         /// </summary>
-        public string Name { get; private set; }
+        public string Name { get; }
 
         /// <summary>
         /// Gets a descriptor for the parameter, or <c>null</c> if this instance
         /// does not represent a parameter.
         /// </summary>
-        public ParameterInfo ParameterInfo { get; private set; }
+        public ParameterInfo ParameterInfo { get; }
 
         /// <inheritdoc />
         public bool Equals(ModelMetadataIdentity other)

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/ModelBindingContext.cs

@@ -156,7 +156,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// by caller when child binding context state should be popped off of
         /// the <see cref="ModelBindingContext"/>.
         /// </summary>
-        public struct NestedScope : IDisposable
+        public readonly struct NestedScope : IDisposable
         {
             private readonly ModelBindingContext _context;
 

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/ModelBindingResult.cs

@@ -9,7 +9,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// <summary>
     /// Contains the result of model binding.
     /// </summary>
-    public struct ModelBindingResult : IEquatable<ModelBindingResult>
+    public readonly struct ModelBindingResult : IEquatable<ModelBindingResult>
     {
         /// <summary>
         /// Creates a <see cref="ModelBindingResult"/> representing a failed model binding operation.

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/ModelStateDictionary.cs

@@ -1003,7 +1003,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             }
         }
 
-        public struct PrefixEnumerable : IEnumerable<KeyValuePair<string, ModelStateEntry>>
+        public readonly struct PrefixEnumerable : IEnumerable<KeyValuePair<string, ModelStateEntry>>
         {
             private readonly ModelStateDictionary _dictionary;
             private readonly string _prefix;
@@ -1136,7 +1136,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             }
         }
 
-        public struct KeyEnumerable : IEnumerable<string>
+        public readonly struct KeyEnumerable : IEnumerable<string>
         {
             private readonly ModelStateDictionary _dictionary;
 
@@ -1191,7 +1191,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             }
         }
 
-        public struct ValueEnumerable : IEnumerable<ModelStateEntry>
+        public readonly struct ValueEnumerable : IEnumerable<ModelStateEntry>
         {
             private readonly ModelStateDictionary _dictionary;
 

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/ValueProviderResult.cs

@@ -25,7 +25,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// regardless of whether a single value or multiple values were submitted.
     /// </para>
     /// </remarks>
-    public struct ValueProviderResult : IEquatable<ValueProviderResult>, IEnumerable<string>
+    public readonly struct ValueProviderResult : IEquatable<ValueProviderResult>, IEnumerable<string>
     {
         private static readonly CultureInfo _invariantCulture = CultureInfo.InvariantCulture;
 

src/Microsoft.AspNetCore.Mvc.Analyzers.Experimental/ApiActionsAreAttributeRoutedFixProvider.cs

@@ -168,7 +168,7 @@ namespace Microsoft.AspNetCore.Mvc.Analyzers
             return false;
         }
 
-        private struct RouteAttributeInfo
+        private readonly struct RouteAttributeInfo
         {
             public RouteAttributeInfo(string name, string type, string[] keywords)
             {

src/Microsoft.AspNetCore.Mvc.ApiExplorer/DefaultApiDescriptionProvider.cs

@@ -659,7 +659,7 @@ namespace Microsoft.AspNetCore.Mvc.ApiExplorer
                 }
             }
 
-            private struct PropertyKey
+            private readonly struct PropertyKey
             {
                 public readonly Type ContainerType;
 

src/Microsoft.AspNetCore.Mvc.Core/Formatters/MediaType.cs

@@ -13,7 +13,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters
     /// <summary>
     /// A media type value.
     /// </summary>
-    public struct MediaType
+    public readonly struct MediaType
     {
         private static readonly StringSegment QualityParameter = new StringSegment("q");
 
@@ -683,7 +683,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters
             }
         }
 
-        private struct MediaTypeParameter : IEquatable<MediaTypeParameter>
+        private readonly struct MediaTypeParameter : IEquatable<MediaTypeParameter>
         {
             public MediaTypeParameter(StringSegment name, StringSegment value)
             {

src/Microsoft.AspNetCore.Mvc.Core/Internal/ClientValidatorCache.cs

@@ -121,7 +121,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             return validators;
         }
 
-        private struct CacheEntry
+        private readonly struct CacheEntry
         {
             public CacheEntry(IReadOnlyList<IClientModelValidator> validators)
             {

src/Microsoft.AspNetCore.Mvc.Core/Internal/ControllerBinderDelegateProvider.cs

@@ -194,7 +194,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             return propertyBindingInfo;
         }
 
-        private struct BinderItem
+        private readonly struct BinderItem
         {
             public BinderItem(IModelBinder modelBinder, ModelMetadata modelMetadata)
             {

src/Microsoft.AspNetCore.Mvc.Core/Internal/FilterCursorItem.cs

@@ -3,7 +3,7 @@
 
 namespace Microsoft.AspNetCore.Mvc.Internal
 {
-    public struct FilterCursorItem<TFilter, TFilterAsync>
+    public readonly struct FilterCursorItem<TFilter, TFilterAsync>
     {
         public FilterCursorItem(TFilter filter, TFilterAsync filterAsync)
         {

src/Microsoft.AspNetCore.Mvc.Core/Internal/FilterFactoryResult.cs

@@ -5,7 +5,7 @@ using Microsoft.AspNetCore.Mvc.Filters;
 
 namespace Microsoft.AspNetCore.Mvc.Internal
 {
-    public struct FilterFactoryResult
+    public readonly struct FilterFactoryResult
     {
         public FilterFactoryResult(
             FilterItem[] cacheableFilters,

src/Microsoft.AspNetCore.Mvc.Core/Internal/MediaTypeSegmentWithQuality.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Internal
     /// <summary>
     /// A media type with its associated quality.
     /// </summary>
-    public struct MediaTypeSegmentWithQuality
+    public readonly struct MediaTypeSegmentWithQuality
     {
         /// <summary>
         /// Initializes an instance of <see cref="MediaTypeSegmentWithQuality"/>.

src/Microsoft.AspNetCore.Mvc.Core/Internal/ValidatorCache.cs

@@ -122,7 +122,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             return validators;
         }
 
-        private struct CacheEntry
+        private readonly struct CacheEntry
         {
             public CacheEntry(IReadOnlyList<IModelValidator> validators)
             {

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Metadata/DefaultModelMetadataProvider.cs

@@ -345,7 +345,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
         {
         }
 
-        private struct ModelMetadataCacheEntry
+        private readonly struct ModelMetadataCacheEntry
         {
             public ModelMetadataCacheEntry(ModelMetadata metadata, DefaultMetadataDetails details)
             {

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/ModelBinderFactory.cs

@@ -310,7 +310,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         // the ParameterDescriptor) or in a call to TryUpdateModel (no BindingInfo) or as a collection element.
         //
         // We need to be able to tell the difference between these things to avoid over-caching.
-        private struct Key : IEquatable<Key>
+        private readonly struct Key : IEquatable<Key>
         {
             private readonly ModelMetadata _metadata;
             private readonly object _token; // Explicitly using ReferenceEquality for tokens.

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Validation/ValidationVisitor.cs

@@ -318,7 +318,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Validation
             return entry;
         }
 
-        protected struct StateManager : IDisposable
+        protected readonly struct StateManager : IDisposable
         {
             private readonly ValidationVisitor _visitor;
             private readonly object _container;

src/Microsoft.AspNetCore.Mvc.Razor/Internal/ViewLocationCacheItem.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Internal
     /// <summary>
     /// An item in <see cref="ViewLocationCacheResult"/>.
     /// </summary>
-    public struct ViewLocationCacheItem
+    public readonly struct ViewLocationCacheItem
     {
         /// <summary>
         /// Initializes a new instance of <see cref="ViewLocationCacheItem"/>.

src/Microsoft.AspNetCore.Mvc.Razor/Internal/ViewLocationCacheKey.cs

@@ -10,7 +10,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Internal
     /// <summary>
     /// Key for entries in <see cref="RazorViewEngine.ViewLookupCache"/>.
     /// </summary>
-    public struct ViewLocationCacheKey : IEquatable<ViewLocationCacheKey>
+    public readonly struct ViewLocationCacheKey : IEquatable<ViewLocationCacheKey>
     {
         /// <summary>
         /// Initializes a new instance of <see cref="ViewLocationCacheKey"/>.

src/Microsoft.AspNetCore.Mvc.Razor/RazorPageFactoryResult.cs

@@ -9,7 +9,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
     /// <summary>
     /// Result of <see cref="IRazorPageFactoryProvider.CreateFactory(string)"/>.
     /// </summary>
-    public struct RazorPageFactoryResult
+    public readonly struct RazorPageFactoryResult
     {
         /// <summary>
         /// Initializes a new instance of <see cref="RazorPageFactoryResult"/> with the

src/Microsoft.AspNetCore.Mvc.Razor/RazorPageResult.cs

@@ -9,7 +9,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
     /// <summary>
     /// Result of locating a <see cref="IRazorPage"/>.
     /// </summary>
-    public struct RazorPageResult
+    public readonly struct RazorPageResult
     {
         /// <summary>
         /// Initializes a new instance of <see cref="RazorPageResult"/> for a successful discovery.

src/Microsoft.AspNetCore.Mvc.RazorPages/Internal/PageBinderFactory.cs

@@ -163,7 +163,7 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Internal
             }
         }
 
-        private struct BinderItem
+        private readonly struct BinderItem
         {
             public BinderItem(IModelBinder modelBinder, ModelMetadata modelMetadata)
             {

src/Microsoft.AspNetCore.Mvc.TagHelpers/Internal/GlobbingUrlBuilder.cs

@@ -352,7 +352,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers.Internal
             return new StringSegment(value.Buffer, offset, trimmedEnd - offset + 1);
         }
 
-        private struct GlobbingUrlKey : IEquatable<GlobbingUrlKey>
+        private readonly struct GlobbingUrlKey : IEquatable<GlobbingUrlKey>
         {
             public GlobbingUrlKey(string include, string exclude)
             {

src/Microsoft.AspNetCore.Mvc.ViewFeatures/Internal/ViewBufferValue.cs

@@ -12,7 +12,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
     /// Encapsulates a string or <see cref="IHtmlContent"/> value.
     /// </summary>
     [DebuggerDisplay("{DebuggerToString()}")]
-    public struct ViewBufferValue
+    public readonly struct ViewBufferValue
     {
         /// <summary>
         /// Initializes a new instance of <see cref="ViewBufferValue"/> with a <c>string</c> value.
@@ -41,15 +41,13 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
         {
             using (var writer = new StringWriter())
             {
-                var valueAsString = Value as string;
+                if (Value is string valueAsString)
-                if (valueAsString != null)
                 {
                     writer.Write(valueAsString);
                     return writer.ToString();
                 }
 
-                var valueAsContent = Value as IHtmlContent;
+                if (Value is IHtmlContent valueAsContent)
-                if (valueAsContent != null)
                 {
                     valueAsContent.WriteTo(writer, HtmlEncoder.Default);
                     return writer.ToString();

src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/MemberExpressionCacheKey.cs

@@ -8,7 +8,7 @@ using System.Reflection;
 
 namespace Microsoft.AspNetCore.Mvc.ViewFeatures
 {
-    internal struct MemberExpressionCacheKey
+    internal readonly struct MemberExpressionCacheKey
     {
         public MemberExpressionCacheKey(Type modelType, MemberExpression memberExpression)
         {
@@ -44,7 +44,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
 
         public MemberInfo[] Members { get; }
 
-        public Enumerator GetEnumerator() => new Enumerator(ref this);
+        public Enumerator GetEnumerator() => new Enumerator(this);
 
         public struct Enumerator
         {
@@ -52,7 +52,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             private int _index;
             private MemberExpression _memberExpression;
 
-            public Enumerator(ref MemberExpressionCacheKey key)
+            public Enumerator(in MemberExpressionCacheKey key)
             {
                 Current = null;
                 _members = key.Members;