https://codefirst.iut.uca.fr/documentation/julien.riboulet/docusaurus/Blazor/edit-item/create-edit-page#route-settings

BlazorApp1/Pages/RouteParameter.razor

@@ -1,13 +1,8 @@
-@page "/RouteParameter/{text?}"
+@page "/RouteParameter/{text}"
 
 <h1>Blazor is @Text!</h1>
 
 @code {
     [Parameter]
     public string? Text { get; set; }
-
-    protected override void OnInitialized()
-    {
-        Text = Text ?? "fantastic";
-    }
 }