Updates

Author: guardrex

aspnetcore/diagnostics/bl0008.md

@@ -17,11 +17,37 @@ uid: diagnostics/bl0008
 
 ## Cause
 
-A property has the [`[SupplyParameterFromForm]` attribute](xref:Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute) and is initialized with a property initializer. 
+A property has the [`[SupplyParameterFromForm]` attribute](xref:Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute) and is initialized with a non-default property initializer, where the initializer can be overwritten with `null` during form submission, causing the `EditForm` to fail with the following exception:
+
+> :::no-loc text="InvalidOperationException: EditForm requires either a Model parameter, or an EditContext parameter, please provide one of these.":::
 
 ## Rule description
 
-The property can be overwritten with `null` when the component receives parameters, causing it to lose its initial value.
+The analyzer warns developers when this pattern is detected, while safely ignoring default value initializers (`null`, `null!`, `default`, `default!`) that don't cause the same issue.
+
+Consider the following `Input` form model with a property initializer:
+
+```csharp
+public class MyComponent : ComponentBase
+{
+    [SupplyParameterFromForm]
+    public InputModel Input { get; set; } = new InputModel();
+}
+```
+
+The analyzer reports the following warning:
+
+> :::no-loc text="Property 'MyComponent.Input' has [SupplyParameterFromForm] and a property initializer. This can be overwritten with null during form posts.":::
+
+<span aria-hidden="true">✔️</span> Safe patterns that are ignored by analyzer:
+
+```csharp
+[SupplyParameterFromForm]
+public InputModel Input { get; set; } = default!;
+
+[SupplyParameterFromForm]
+public InputModel Input { get; set; } = null!;
+```
 
 ## How to fix violations