Async requiring you return Task/Task<T>/void =( Trying to make Get[] work for both Async and non-async, but since using the async keyword requires you to return void/Task/Task<T> and since you cannot overload based on return type.. we're screwed. You cannot even return a type, which can be implicitly cast to Task/Task<T> because you'll get a com…

gistfile1.txt

    using System;
    using System.Collections.Generic;
    using System.Net.Http;
    using System.Threading.Tasks;
    using Xunit;

    public class Fixture
    {
        [Fact]
        public void Should_FactMethodName()
        {
            var module = new Class1();

            var result = module.routes["/"].Invoke(new object());

            var i = 10;
        }
    }

    public class Class1 : Module
    {
        public Class1()
        {
            Get["/"] = x =>
            {
                return "non async";
            };

            Get["/stuff"] = async x =>
            {
                var client = new HttpClient();
                var result = await client.GetAsync("http://www.nancyfx.org");
                var content = await result.Content.ReadAsStringAsync();
                return content;
            };
        }
    }

    public class Module
    {
        public readonly IDictionary<string, Func<dynamic, dynamic>> routes = new Dictionary<string, Func<dynamic, dynamic>>();

        public Builder Get
        {
            get { return new Builder(this); }
        }

        public class Builder
        {
            private readonly Module module;

            public Builder(Module module)
            {
                this.module = module;
            }

            //public Func<dynamic, dynamic> this[string path]
            //{
            //    set { this.module.routes.Add(path, value); }
            //}

            public Func<dynamic, Task<dynamic>> this[string path]
            {
                set { this.module.routes.Add(path, value); }
            }
        }
    }

What about forcing return type as Task<dynamic>. This is a huge breaking change though. but might be worth it.

Get["/"] = _ => Task.FromResult("hi");

Task.FromResult is only present in .net 4.5+, so adding a helper method in NancyModule could be good.

Get["/"] = _ => ToTask("hi");

ToTask is a helper method.

private Task<T> ToTask<T>(T value) {
     var tcs = new TaskCompletionSource<T>();
     tcs.TrySetResult(value);
     return tcs.Task;
}