Put back the earlier EditForm behavior of using an empty-string handler name for now

Author: SteveSandersonMS

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.EventDispatch.cs

@@ -14,18 +14,18 @@ internal partial class EndpointHtmlRenderer
 
     internal Task DispatchSubmitEventAsync(string? handlerName)
     {
-        if (string.IsNullOrEmpty(handlerName))
+        if (handlerName is null)
         {
             // Currently this also happens if you forget to add the hidden field, but soon we'll do that automatically, so the
             // message is designed around that.
-            throw new InvalidOperationException($"Cannot dispatch the POST request to the Razor Component endpoint, because the POST data does not specify which form is being submitted. To fix this, ensure form elements have an @onsubmit:name attribute with any unique value, or pass a Name parameter if using EditForm.");
+            throw new InvalidOperationException($"Cannot dispatch the POST request to the Razor Component endpoint, because the POST data does not specify which form is being submitted. To fix this, ensure form elements have an @onsubmit:name attribute with any unique value, or pass a FormHandlerName parameter if using EditForm.");
         }
 
         if (!_namedSubmitEventsByAssignedName.TryGetValue(handlerName, out var frameLocation))
         {
             // This might only be possible if you deploy an app update and someone tries to submit
             // an old version of a form, and your new app no longer has a matching name
-            throw new InvalidOperationException($"Cannot submit the form '{handlerName}' because no submit handler was found with that name. Ensure forms have a unique @onsubmit:name attribute, or pass the Name parameter if using EditForm.");
+            throw new InvalidOperationException($"Cannot submit the form '{handlerName}' because no submit handler was found with that name. Ensure forms have a unique @onsubmit:name attribute, or pass the FormHandlerName parameter if using EditForm.");
         }
 
         var eventHandlerId = FindEventHandlerIdForNamedEvent("onsubmit", frameLocation.ComponentId, frameLocation.FrameIndex);

src/Components/Web/src/Forms/EditForm.cs

@@ -172,16 +172,20 @@ void RenderFormContents(RenderTreeBuilder builder, FormMappingContext? bindingCo
 
             builder.AddMultipleAttributes(4, AdditionalAttributes);
             builder.AddAttribute(5, "onsubmit", _handleSubmitDelegate);
-            builder.OpenComponent<CascadingValue<EditContext>>(6);
-            builder.AddComponentParameter(7, "IsFixed", true);
-            builder.AddComponentParameter(8, "Value", _editContext);
+            if (bindingContext != null)
+            {
+                builder.AddNamedEvent(6, "onsubmit", bindingContext.Name);
+            }
+            builder.OpenComponent<CascadingValue<EditContext>>(7);
+            builder.AddComponentParameter(8, "IsFixed", true);
+            builder.AddComponentParameter(9, "Value", _editContext);
             if (bindingContext != null && !OperatingSystem.IsBrowser())
             {
-                builder.AddComponentParameter(9, "ChildContent", _renderWithBindingValidator);
+                builder.AddComponentParameter(10, "ChildContent", _renderWithBindingValidator);
             }
             else
             {
-                builder.AddComponentParameter(10, "ChildContent", ChildContent?.Invoke(_editContext));
+                builder.AddComponentParameter(11, "ChildContent", ChildContent?.Invoke(_editContext));
             }
             builder.CloseComponent();
             builder.CloseElement();