C# Blazor: How to use a dynamic @typeparam in Code behind?

Question

I would like to know, how it is possible to call a component with a @typeparam which comes from the URL

As it has been already discussed in C# Blazor: How to use @typeparam in Code behind? (with workaround), I built a component like Roger Wolf did in his solution.

Raozor.cs using Microsoft.AspNetCore.Components;

namespace BlazorApp1.Components
{
    public partial class MyCustomComponent<T> : ComponentBase
    {
        [Parameter]
        public string Label { get; set; }
    }
}

The Razor part:

@namespace BlazorApp1.Components
@typeparam T
<label>@($"{Label}. Provided type is {typeof(T).Name.ToUpper()}")</label>

Index.razor page

@page "/{typeName}"
@using BlazorApp1.Components

<MyCustomComponent T="@TypeName" Label="Custom component label" />
@code
{
    [Parameter]
    public string TypeName {get; set;}
}

So the Line where I try to set the Type by the string property I get en compiler error. (I guess that internal an typeof() function will determine the type for the component class.) It will only compile, if I use an fixed coded type. :

e.g.: <MyCustomComponent T="long" Label="Custom component label" />

What I want to do is pull the type parameter from URL. Any ideas to get this work?

agua from mars · Accepted Answer · 2020-03-28 15:17:08Z

1

The type of @typeparam is deduce at compile time and you should have a parameter of type T in your component:

namespace BlazorApp1.Components
{
    public partial class MyCustomComponent<T> : ComponentBase
    {
        [Parameter]
        public T MyParameter { get; set; }
    }
}

It's use to make generic component, you cannot use it as your sample.

answered Mar 28, 2020 at 15:17

agua from mars

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