Quick fix: Address a couple of nits in / around `ViewDataDictionary`

- remove duplicate `null` checks in `ViewDataDictionary` constructors
- correct a couple of code comments
- use a `public` constructor for `ViewDataDictionary` in `ViewExecutor`

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

@@ -4,8 +4,8 @@
 using System;
 using System.Collections.Concurrent;
 using System.Diagnostics;
-using System.Reflection;
 using System.Linq.Expressions;
+using System.Reflection;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.AspNetCore.Mvc.Razor.Internal;
 using Microsoft.AspNetCore.Mvc.Rendering;
@@ -66,7 +66,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         private ViewDataDictionary CreateViewDataDictionary(ViewContext context, PageActivationInfo activationInfo)
         {
             // Create a ViewDataDictionary<TModel> if the ViewContext.ViewData is not set or the type of
-            // ViewContext.ViewData is an incompatibile type.
+            // ViewContext.ViewData is an incompatible type.
             if (context.ViewData == null)
             {
                 // Create ViewDataDictionary<TModel>(IModelMetadataProvider, ModelStateDictionary).

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

@@ -33,14 +33,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             ModelStateDictionary modelState)
             : this(metadataProvider, modelState, declaredModelType: typeof(object))
         {
-            if (metadataProvider == null)
-            {
-                throw new ArgumentNullException(nameof(metadataProvider));
-            }
-            if (modelState == null)
-            {
-                throw new ArgumentNullException(nameof(modelState));
-            }
         }
 
         /// <summary>
@@ -56,10 +48,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         public ViewDataDictionary(ViewDataDictionary source)
             : this(source, source.Model, source._declaredModelType)
         {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
         }
 
         /// <summary>
@@ -77,10 +65,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         public ViewDataDictionary(ViewDataDictionary source, object model)
             : this(source, model, declaredModelType: typeof(object))
         {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
         }
 
         /// <summary>
@@ -94,10 +78,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         internal ViewDataDictionary(IModelMetadataProvider metadataProvider)
             : this(metadataProvider, new ModelStateDictionary())
         {
-            if (metadataProvider == null)
-            {
-                throw new ArgumentNullException(nameof(metadataProvider));
-            }
         }
 
         /// <summary>
@@ -119,14 +99,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             Type declaredModelType)
             : this(metadataProvider, new ModelStateDictionary(), declaredModelType)
         {
-            if (metadataProvider == null)
-            {
-                throw new ArgumentNullException(nameof(metadataProvider));
-            }
-            if (declaredModelType == null)
-            {
-                throw new ArgumentNullException(nameof(declaredModelType));
-            }
         }
 
         /// <summary>
@@ -198,10 +170,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         protected ViewDataDictionary(ViewDataDictionary source, Type declaredModelType)
             : this(source, model: source.Model, declaredModelType: declaredModelType)
         {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
         }
 
         /// <summary>

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

@@ -1,7 +1,6 @@
 // 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 Microsoft.AspNetCore.Mvc.ModelBinding;
 
 namespace Microsoft.AspNetCore.Mvc.ViewFeatures
@@ -15,20 +14,12 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         /// For use when creating a <see cref="ViewDataDictionary{TModel}"/> for a new top-level scope.
         /// </remarks>
         /// <inheritdoc />
-        // References may not show up due to ActivatorUtilities use in RazorPageActivator.
+        // References may not show up due to Type.GetConstructor() use in RazorPageActivator.
         public ViewDataDictionary(
             IModelMetadataProvider metadataProvider,
             ModelStateDictionary modelState)
             : base(metadataProvider, modelState, declaredModelType: typeof(TModel))
         {
-            if (metadataProvider == null)
-            {
-                throw new ArgumentNullException(nameof(metadataProvider));
-            }
-            if (modelState == null)
-            {
-                throw new ArgumentNullException(nameof(modelState));
-            }
         }
 
         /// <summary>
@@ -48,14 +39,10 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         /// </para>
         /// </remarks>
         /// <inheritdoc />
-        // References may not show up due to ActivatorUtilities use in RazorPageActivator.
+        // References may not show up due to Type.GetConstructor() use in RazorPageActivator.
         public ViewDataDictionary(ViewDataDictionary source)
             : base(source, declaredModelType: typeof(TModel))
         {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
         }
 
         /// <summary>
@@ -80,10 +67,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         public ViewDataDictionary(ViewDataDictionary source, object model)
             : base(source, model, declaredModelType: typeof(TModel))
         {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
         }
 
         /// <summary>
@@ -94,10 +77,6 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         internal ViewDataDictionary(IModelMetadataProvider metadataProvider)
             : base(metadataProvider, declaredModelType: typeof(TModel))
         {
-            if (metadataProvider == null)
-            {
-                throw new ArgumentNullException(nameof(metadataProvider));
-            }
         }
 
         public new TModel Model

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

@@ -130,11 +130,11 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
                 throw new ArgumentNullException(nameof(view));
             }
 
-            var services = actionContext.HttpContext.RequestServices;
             if (viewData == null)
             {
+                var services = actionContext.HttpContext.RequestServices;
                 var metadataProvider = services.GetRequiredService<IModelMetadataProvider>();
-                viewData = new ViewDataDictionary(metadataProvider);
+                viewData = new ViewDataDictionary(metadataProvider, actionContext.ModelState);
             }
 
             if (tempData == null)