C# 11 Static Endpoint Mapping

IEndpointDefinition.cs

public interface IEndpointDefinition
{
    static abstract void MapEndpoint(IEndpointRouteBuilder builder);
}

public static class EndpointRouteBuilderExtensions
{
    private static readonly MethodInfo MapEndpointMethod = typeof(EndpointRouteBuilderExtensions).GetMethod(nameof(MapEndpoint), BindingFlags.NonPublic | BindingFlags.Static)!;
    private static void MapEndpoint<T>(IEndpointRouteBuilder builder) where T : IEndpointDefinition => T.MapEndpoint(builder);

    public static void MapEndpointDefinitionsFromAssemblyContaining<T>(this IEndpointRouteBuilder e) => MapEndpointDefinitiionsFromAssembly(e, typeof(T).Assembly);
    public static void MapEndpointDefinitiionsFromAssembly(this IEndpointRouteBuilder builder, Assembly assembly)
    {
        ArgumentNullException.ThrowIfNull(builder);
        ArgumentNullException.ThrowIfNull(assembly);

        var endpointDefinitions = assembly.GetTypes().Where(t => typeof(IEndpointDefinition).IsAssignableFrom(t) && !t.IsInterface);
        foreach (var endpointDefinition in endpointDefinitions)
        {
            MapEndpointMethod.MakeGenericMethod(endpointDefinition).Invoke(null, new[] { builder });
        }
    }
}

Ping.cs

public class Ping : IRequest<string> { }

public class PingHandler : IRequestHandler<Ping, string>, IEndpointDefinition
{
    public static void MapEndpoint(IEndpointRouteBuilder builder) => builder
        .MapGet("/ping", ([FromServices] IMediator mediator, [AsParameters] Ping ping) => mediator.Send(ping));

    public Task<string> Handle(Ping request, CancellationToken cancellationToken)
    {
        return Task.FromResult("Pong");
    }
}

Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddMediatR(Assembly.GetExecutingAssembly());
builder.Services.AddScoped<PingHandler>();

var app = builder.Build();

app.MapEndpointDefinitionsFromAssemblyContaining<Program>();

app.Run();