How to initialize a Blazor Component as Page with Generics

Question

I habe a base Blazor component, using two generic classes like this

(base.razor)
@typeparam T where T : class
@typeparam P where P : class
...

(base.razor.cs)
public abstract partial class BaseClass<T, P> : ComponentBase where T : class where P : class
{
     [Parameter] public P? CurrentParent { get; set; }
...

I can easily load a derived class with a wrapper component like this:

@page "/mypage"

<Derived T="Class1" P="Class2" />
...

with this derived component:

@inherits BaseClass<T,P>
@{
    base.BuildRenderTree(__builder);
}
@code {
    @typeparam T where T : Class1
    @typeparam P where P : Class2

But when I try to call this derived component directly, with a @page it fails

@page "/direct"
@inherits BaseClass<T,P>
@{
    base.BuildRenderTree(__builder);
}
@code {
    @typeparam T where T : Class1
    @typeparam P where P : Class2

Trying to call the page in this way I get the following exception:

System.ArgumentException: Cannot create an instance of ...Pages.Derived`2[T,P] because Type.ContainsGenericParameters is true

I expect this is because the Parameter P is not given, can someone point me in the right direction of how to handle this without specifying the parameter or how to specify it?

Answer 1

When the page is called from somewhere else, the P and T types can't be left open.

This ought to work:

@page "/direct"
@inherits BaseClass<Class1,Class2>
@{
    base.BuildRenderTree(__builder);
}
@code {
 //   @typeparam T where T : Class1
 //   @typeparam P where P : Class2