Move CascadingParameterAttributeBase.Name into subclasses. It shouldn't have been in the base because the meaning varies.

Author: SteveSandersonMS

src/Components/Components/src/CascadingParameterAttribute.cs

@@ -20,5 +20,5 @@ public sealed class CascadingParameterAttribute : CascadingParameterAttributeBas
     /// <see cref="CascadingValue{T}"/>  that supplies a value with a compatible
     /// type.
     /// </summary>
-    public override string? Name { get; set; }
+    public string? Name { get; set; }
 }

src/Components/Components/src/CascadingParameterAttributeBase.cs

@@ -8,12 +8,6 @@ namespace Microsoft.AspNetCore.Components;
 /// </summary>
 public abstract class CascadingParameterAttributeBase : Attribute
 {
-    /// <summary>
-    /// Gets or sets the name for the parameter, which correlates to the name
-    /// of a cascading value.
-    /// </summary>
-    public abstract string? Name { get; set; }
-
     /// <summary>
     /// Gets a flag indicating whether the cascading parameter should
     /// be supplied only once per component.

src/Components/Components/src/PublicAPI.Unshipped.txt

@@ -1,6 +1,4 @@
 #nullable enable
-abstract Microsoft.AspNetCore.Components.CascadingParameterAttributeBase.Name.get -> string?
-abstract Microsoft.AspNetCore.Components.CascadingParameterAttributeBase.Name.set -> void
 abstract Microsoft.AspNetCore.Components.RenderModeAttribute.Mode.get -> Microsoft.AspNetCore.Components.IComponentRenderMode!
 Microsoft.AspNetCore.Components.CascadingParameterAttributeBase
 Microsoft.AspNetCore.Components.CascadingParameterAttributeBase.CascadingParameterAttributeBase() -> void
@@ -83,20 +81,12 @@ Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddComponentParamete
 Microsoft.AspNetCore.Components.StreamRenderingAttribute
 Microsoft.AspNetCore.Components.StreamRenderingAttribute.Enabled.get -> bool
 Microsoft.AspNetCore.Components.StreamRenderingAttribute.StreamRenderingAttribute(bool enabled) -> void
-*REMOVED*Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.get -> string?
-*REMOVED*Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.set -> void
 Microsoft.AspNetCore.Components.SupplyParameterFromQueryProviderServiceCollectionExtensions
 Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionExtensions
-override Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.get -> string?
-override Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.set -> void
 override Microsoft.AspNetCore.Components.EventCallback.GetHashCode() -> int
 override Microsoft.AspNetCore.Components.EventCallback.Equals(object? obj) -> bool
 override Microsoft.AspNetCore.Components.EventCallback<TValue>.GetHashCode() -> int
 override Microsoft.AspNetCore.Components.EventCallback<TValue>.Equals(object? obj) -> bool
-*REMOVED*Microsoft.AspNetCore.Components.SupplyParameterFromQueryAttribute.Name.get -> string?
-*REMOVED*Microsoft.AspNetCore.Components.SupplyParameterFromQueryAttribute.Name.set -> void
-override Microsoft.AspNetCore.Components.SupplyParameterFromQueryAttribute.Name.get -> string?
-override Microsoft.AspNetCore.Components.SupplyParameterFromQueryAttribute.Name.set -> void
 static Microsoft.AspNetCore.Components.SupplyParameterFromQueryProviderServiceCollectionExtensions.AddSupplyValueFromQueryProvider(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
 static Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionExtensions.AddCascadingValue<TValue>(this Microsoft.Extensions.DependencyInjection.IServiceCollection! serviceCollection, string! name, System.Func<System.IServiceProvider!, TValue>! valueFactory) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
 static Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionExtensions.AddCascadingValue<TValue>(this Microsoft.Extensions.DependencyInjection.IServiceCollection! serviceCollection, System.Func<System.IServiceProvider!, Microsoft.AspNetCore.Components.CascadingValueSource<TValue>!>! sourceFactory) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!

src/Components/Components/src/Reflection/ComponentProperties.cs

@@ -184,8 +184,7 @@ private static void ThrowForUnknownIncomingParameterName([DynamicallyAccessedMem
             {
                 throw new InvalidOperationException(
                     $"Object of type '{targetType.FullName}' has a property matching the name '{parameterName}', " +
-                    $"but it does not have [{nameof(ParameterAttribute)}], [{nameof(CascadingParameterAttribute)}] or " +
-                    $"[SupplyParameterFromFormAttribute] applied.");
+                    $"but it does not have [Parameter], [CascadingParameter], or any other parameter-supplying attribute.");
             }
             else
             {

src/Components/Components/src/SupplyParameterFromQueryAttribute.cs

@@ -14,5 +14,5 @@ public sealed class SupplyParameterFromQueryAttribute : CascadingParameterAttrib
     /// Gets or sets the name of the querystring parameter. If null, the querystring
     /// parameter is assumed to have the same name as the associated property.
     /// </summary>
-    public override string? Name { get; set; }
+    public string? Name { get; set; }
 }

src/Components/Components/src/SupplyParameterFromQueryProviderServiceCollectionExtensions.cs

@@ -50,7 +50,8 @@ public bool CanSupplyValue(in CascadingParameterInfo parameterInfo)
                 UpdateQueryParameters();
             }
 
-            var queryParameterName = parameterInfo.Attribute.Name ?? parameterInfo.PropertyName;
+            var attribute = (SupplyParameterFromQueryAttribute)parameterInfo.Attribute; // Must be a valid cast because we check in CanSupplyValue
+            var queryParameterName = attribute.Name ?? parameterInfo.PropertyName;
             return _queryParameterValueSupplier.GetQueryParameterValue(parameterInfo.PropertyType, queryParameterName);
         }
 

src/Components/Components/test/CascadingParameterStateTest.cs

@@ -476,8 +476,6 @@ class ComponentWithNamedCascadingParam : TestComponentBase
 
     class SupplyParameterWithSingleDeliveryAttribute : CascadingParameterAttributeBase
     {
-        public override string Name { get; set; }
-
         internal override bool SingleDelivery => true;
     }
 
@@ -523,19 +521,3 @@ public TestNavigationManager()
         }
     }
 }
-
-[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
-public sealed class SupplyParameterFromFormAttribute : CascadingParameterAttributeBase
-{
-    /// <summary>
-    /// Gets or sets the name for the parameter. The name is used to match
-    /// the form data and decide whether or not the value needs to be bound.
-    /// </summary>
-    public override string Name { get; set; }
-
-    /// <summary>
-    /// Gets or sets the name for the handler. The name is used to match
-    /// the form data and decide whether or not the value needs to be bound.
-    /// </summary>
-    public string Handler { get; set; }
-}

src/Components/Components/test/CascadingParameterTest.cs

@@ -734,8 +734,6 @@ private class SingleDeliveryValue(string text)
 
     private class SingleDeliveryCascadingParameterAttribute : CascadingParameterAttributeBase
     {
-        public override string Name { get; set; }
-
         internal override bool SingleDelivery => true;
     }
 
@@ -852,13 +850,11 @@ class SecondCascadingParameterConsumerComponent<T1, T2> : CascadingParameterCons
     [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
     class CustomCascadingParameter1Attribute : CascadingParameterAttributeBase
     {
-        public override string Name { get; set; }
     }
 
     [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
     class CustomCascadingParameter2Attribute : CascadingParameterAttributeBase
     {
-        public override string Name { get; set; }
     }
 
     class CustomCascadingValueProducer<TAttribute> : AutoRenderComponent, ICascadingValueSupplier
@@ -904,7 +900,7 @@ void ICascadingValueSupplier.Unsubscribe(ComponentState subscriber, in Cascading
 
     class CustomCascadingValueConsumer1 : AutoRenderComponent
     {
-        [CustomCascadingParameter1(Name = nameof(Value))]
+        [CustomCascadingParameter1]
         public object Value { get; set; }
 
         protected override void BuildRenderTree(RenderTreeBuilder builder)
@@ -915,7 +911,7 @@ protected override void BuildRenderTree(RenderTreeBuilder builder)
 
     class CustomCascadingValueConsumer2 : AutoRenderComponent
     {
-        [CustomCascadingParameter2(Name = nameof(Value))]
+        [CustomCascadingParameter2]
         public object Value { get; set; }
 
         protected override void BuildRenderTree(RenderTreeBuilder builder)

src/Components/Components/test/ParameterViewTest.Assignment.cs

@@ -183,7 +183,7 @@ public void IncomingParameterMatchesPropertyNotDeclaredAsParameter_Throws()
         Assert.Equal(default, target.IntProp);
         Assert.Equal(
             $"Object of type '{typeof(HasPropertyWithoutParameterAttribute).FullName}' has a property matching the name '{nameof(HasPropertyWithoutParameterAttribute.IntProp)}', " +
-            $"but it does not have [{nameof(ParameterAttribute)}], [{nameof(CascadingParameterAttribute)}] or [{nameof(SupplyParameterFromFormAttribute)}] applied.",
+            "but it does not have [Parameter], [CascadingParameter], or any other parameter-supplying attribute.",
             ex.Message);
     }
 

src/Components/Web/src/Forms/Mapping/SupplyParameterFromFormValueProvider.cs

@@ -73,8 +73,9 @@ void ICascadingValueSupplier.Unsubscribe(ComponentState subscriber, in Cascading
     {
         Debug.Assert(mappingContext != null);
 
-        var parameterName = parameterInfo.Attribute.Name ?? parameterInfo.PropertyName;
-        var restrictToFormName = ((SupplyParameterFromFormAttribute)parameterInfo.Attribute).Handler;
+        var attribute = (SupplyParameterFromFormAttribute)parameterInfo.Attribute; // Must be a valid cast because we check in CanSupplyValue
+        var parameterName = attribute.Name ?? parameterInfo.PropertyName;
+        var restrictToFormName = attribute.Handler;
         Action<string, FormattableString, string?> errorHandler = string.IsNullOrEmpty(restrictToFormName) ?
             mappingContext.AddError :
             (name, message, value) => mappingContext.AddError(restrictToFormName, parameterName, message, value);

src/Components/Web/src/PublicAPI.Unshipped.txt

@@ -65,6 +65,8 @@ Microsoft.AspNetCore.Components.HtmlRendering.Infrastructure.StaticHtmlRenderer.
 Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute
 Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute.Handler.get -> string?
 Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute.Handler.set -> void
+Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute.Name.get -> string?
+Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute.Name.set -> void
 Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute.SupplyParameterFromFormAttribute() -> void
 Microsoft.AspNetCore.Components.Web.AutoRenderMode
 Microsoft.AspNetCore.Components.Web.AutoRenderMode.AutoRenderMode() -> void
@@ -111,8 +113,6 @@ override Microsoft.AspNetCore.Components.Forms.Editor<T>.OnParametersSet() -> vo
 override Microsoft.AspNetCore.Components.HtmlRendering.Infrastructure.StaticHtmlRenderer.Dispatcher.get -> Microsoft.AspNetCore.Components.Dispatcher!
 override Microsoft.AspNetCore.Components.HtmlRendering.Infrastructure.StaticHtmlRenderer.HandleException(System.Exception! exception) -> void
 override Microsoft.AspNetCore.Components.HtmlRendering.Infrastructure.StaticHtmlRenderer.UpdateDisplayAsync(in Microsoft.AspNetCore.Components.RenderTree.RenderBatch renderBatch) -> System.Threading.Tasks.Task!
-override Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute.Name.get -> string?
-override Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute.Name.set -> void
 override Microsoft.AspNetCore.Components.Web.RenderModeAutoAttribute.Mode.get -> Microsoft.AspNetCore.Components.IComponentRenderMode!
 override Microsoft.AspNetCore.Components.Web.RenderModeServerAttribute.Mode.get -> Microsoft.AspNetCore.Components.IComponentRenderMode!
 override Microsoft.AspNetCore.Components.Web.RenderModeWebAssemblyAttribute.Mode.get -> Microsoft.AspNetCore.Components.IComponentRenderMode!

src/Components/Web/src/SupplyParameterFromFormAttribute.cs

@@ -11,11 +11,9 @@ namespace Microsoft.AspNetCore.Components;
 public sealed class SupplyParameterFromFormAttribute : CascadingParameterAttributeBase
 {
     /// <summary>
-    /// Gets or sets the name for the parameter. The name is used to determine
-    /// the prefix to use to match the form data and decide whether or not the
-    /// value needs to be bound.
+    /// Gets or sets the name for the form value. If not specified, the property name will be used.
     /// </summary>
-    public override string? Name { get; set; }
+    public string? Name { get; set; }
 
     /// <summary>
     /// Gets or sets the name for the handler. The name is used to match