Background and Motivation

EndpointMetadataCollection has a GetMetadata<T>() method:

public T? GetMetadata<T> () where T : class;

https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.endpointmetadatacollection.getmetadata?view=aspnetcore-6.0#microsoft-aspnetcore-http-endpointmetadatacollection-getmetadata-1

It returns null if there is no matching metadata. It would be useful to have a GetRequiredMetadata<T>() method that returns a value or throws.

Proposed API

namespace Microsoft.AspNetCore.Http
{
    public class EndpointMetadataCollection
    {
+       public T GetRequiredMetadata<T> () where T : class;
    }
}

The method would function the same as getting a required service from DI or a required feature from a feature collection.

Usage Examples

endpoints.MapGet("/", context =>
{
    var endpoint = context.GetEndpoint();
    var requiredMetadata = endpoint.Metadata.GetRequiredMetadata<MyMetadata>();
});

Alternative Designs

Risks