Add support general delegate types

This builds upon existing support for UIEventHandler-typed component
properties and applies the same principle to any delegate type.

We try to help by generating the LSH of the lambda `=>` allowing you to
write `OnClick="Foo()"` rather than `OnClick="(e) => Foo()"`. You can of
course use @ as an escape.

The only rough edge here is that if the parameter names aren't memorable
for the delgate type, it's not super helpful.

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorDesignTimeNodeWriter.cs

@@ -423,7 +423,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                 // We don't expect this to happen, we just want to know if it can.
                 throw new InvalidOperationException("Attribute nodes should either be minimized or a single content node.");
             }
-            else if (node.BoundAttribute.IsUIEventHandlerProperty())
+            else if (node.BoundAttribute.IsDelegateProperty())
             {
                 // See the runtime version of this code for a thorough description of what we're doing here
                 if ((cSharpNode = node.Children[0] as CSharpExpressionIntermediateNode) != null)
@@ -445,7 +445,9 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                     context.CodeWriter.Write(" = ");
                     context.CodeWriter.Write("new ");
                     context.CodeWriter.Write(node.BoundAttribute.TypeName);
-                    context.CodeWriter.Write("(e => ");
+                    context.CodeWriter.Write("(");
+                    context.CodeWriter.Write(node.BoundAttribute.GetDelegateSignature());
+                    context.CodeWriter.Write(" => ");
                     WriteCSharpToken(context, ((IntermediateToken)node.Children[0]));
                     context.CodeWriter.Write(");");
                     context.CodeWriter.WriteLine();

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorRuntimeNodeWriter.cs

@@ -470,7 +470,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                 // We don't expect this to happen, we just want to know if it can.
                 throw new InvalidOperationException("Attribute nodes should either be minimized or a single content node.");
             }
-            else if (node.BoundAttribute.IsUIEventHandlerProperty())
+            else if (node.BoundAttribute.IsDelegateProperty())
             {
                 // This is a UIEventHandler property. We do some special code generation for this
                 // case so that it's easier to write for common cases.
@@ -502,7 +502,8 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                     context.CodeWriter.Write("new ");
                     context.CodeWriter.Write(node.BoundAttribute.TypeName);
                     context.CodeWriter.Write("(");
-                    context.CodeWriter.Write("e => ");
+                    context.CodeWriter.Write(node.BoundAttribute.GetDelegateSignature());
+                    context.CodeWriter.Write(" => ");
                     context.CodeWriter.Write(((IntermediateToken)node.Children[0]).Content);
                     context.CodeWriter.Write(")");
                 }

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/ComponentTagHelperDescriptorProvider.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Razor;
@@ -11,7 +12,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
 {
     internal class ComponentTagHelperDescriptorProvider : RazorEngineFeatureBase, ITagHelperDescriptorProvider
     {
-        public static readonly string UIEventHandlerPropertyMetadata = "Blazor.IsUIEventHandler";
+        public static readonly string DelegateSignatureMetadata = "Blazor.DelegateSignature";
 
         public readonly static string ComponentTagHelperKind = ComponentDocumentClassifierPass.ComponentDocumentKind;
         
@@ -113,7 +114,11 @@ namespace Microsoft.AspNetCore.Blazor.Razor
 
                     if (property.kind == PropertyKind.Delegate)
                     {
-                        pb.Metadata.Add(UIEventHandlerPropertyMetadata, bool.TrueString);
+                        var propertyType = (INamedTypeSymbol)property.property.Type;
+                        var parameters = propertyType.DelegateInvokeMethod.Parameters;
+
+                        var signature = "(" + string.Join(", ", parameters.Select(p => p.Name)) + ")";
+                        pb.Metadata.Add(DelegateSignatureMetadata, signature);
                     }
 
                     xml = property.property.GetDocumentationCommentXml();
@@ -182,12 +187,8 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                         kind = PropertyKind.Enum;
                     }
 
-                    if (kind == PropertyKind.Default &&
+                    if (kind == PropertyKind.Default && property.Type.TypeKind == TypeKind.Delegate)
-                        property.Type.TypeKind == TypeKind.Delegate &&
-                        property.Type.ToDisplayString(FullNameTypeDisplayFormat) == BlazorApi.UIEventHandler.FullTypeName)
                     {
-                        // For delegate types we do some special code generation when the type
-                        // UIEventHandler.
                         kind = PropertyKind.Delegate;
                     }
 

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/TagHelperBoundAttributeDescriptorExtensions.cs

@@ -8,17 +8,27 @@ namespace Microsoft.AspNetCore.Blazor.Razor
 {
     internal static class TagHelperBoundAttributeDescriptorExtensions
     {
-        public static bool IsUIEventHandlerProperty(this BoundAttributeDescriptor attribute)
+        public static bool IsDelegateProperty(this BoundAttributeDescriptor attribute)
         {
             if (attribute == null)
             {
                 throw new ArgumentNullException(nameof(attribute));
             }
 
-            var key = ComponentTagHelperDescriptorProvider.UIEventHandlerPropertyMetadata;
+            var key = ComponentTagHelperDescriptorProvider.DelegateSignatureMetadata;
-            return 
+            return attribute.Metadata.TryGetValue(key, out var value);
-                attribute.Metadata.TryGetValue(key, out var value) && 
+        }
-                string.Equals(value, bool.TrueString);
+
+        public static string GetDelegateSignature(this BoundAttributeDescriptor attribute)
+        {
+            if (attribute == null)
+            {
+                throw new ArgumentNullException(nameof(attribute));
+            }
+
+            var key = ComponentTagHelperDescriptorProvider.DelegateSignatureMetadata;
+            attribute.Metadata.TryGetValue(key, out var value);
+            return value;
         }
     }
 }

test/Microsoft.AspNetCore.Blazor.Build.Test/DesignTimeCodeGenerationRazorIntegrationTest.cs

@@ -239,7 +239,7 @@ global::System.Object __typeHelper = ""*, TestAssembly"";
         {
             base.BuildRenderTree(builder);
 
-            __o = new Microsoft.AspNetCore.Blazor.UIEventHandler(e => 
+            __o = new Microsoft.AspNetCore.Blazor.UIEventHandler(eventArgs => 
 #line 2 ""x:\dir\subdir\Test\TestComponent.cshtml""
                       Increment()
 

test/Microsoft.AspNetCore.Blazor.Build.Test/RuntimeCodeGenerationRazorIntegrationTest.cs

@@ -225,7 +225,7 @@ namespace Test
         {
             base.BuildRenderTree(builder);
             builder.OpenComponent<Test.MyComponent>(0);
-            builder.AddAttribute(1, ""OnClick"", new Microsoft.AspNetCore.Blazor.UIEventHandler(e => Increment()));
+            builder.AddAttribute(1, ""OnClick"", new Microsoft.AspNetCore.Blazor.UIEventHandler(eventArgs => Increment()));
             builder.CloseComponent();
             builder.AddContent(2, ""\n\n"");
         }

test/Microsoft.AspNetCore.Blazor.Razor.Extensions.Test/ComponentTagHelperDescriptorProviderTest.cs

@@ -282,8 +282,8 @@ namespace Test
             Assert.False(attribute.IsStringProperty);
         }
 
-        [Fact] // UIEventHandler properties have some special intellisense behavior
+        [Fact]
-        public void Excecute_UIEventHandlerProperty_CreatesDescriptor()
+        public void Execute_DelegateProperty_CreatesDescriptor()
         {
             // Arrange
 
@@ -326,7 +326,7 @@ namespace Test
             Assert.False(attribute.IsBooleanProperty);
             Assert.False(attribute.IsEnum);
             Assert.False(attribute.IsStringProperty);
-            Assert.True(attribute.IsUIEventHandlerProperty());
+            Assert.True(attribute.IsDelegateProperty());
         }
 
         // For simplicity in testing, exlude the built-in components. We'll add more and we