To search for asynchronous APIs, create a console app with this code. Reference all dlls you want to search, and then run the app in the debugger.

Program.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;

namespace DisplayAsyncAPIs
{
    class Program
    {
        static void Main(string[] args)
        {
            var assemblies = AppDomain.CurrentDomain.GetAssemblies();
            Console.WriteLine("Searching " + assemblies.Length + " assemblies...");
            var apis = AppDomain.CurrentDomain.GetAssemblies()
                .SelectMany(x =>
                {
                    try { return x.GetTypes(); }
                    catch (ReflectionTypeLoadException ex)
                    { return ex.Types.Where(t => t != null); }
                }).Where(x => x.IsPublic || x.IsNestedFamily || x.IsNestedFamORAssem)
                .SelectMany(x => x.GetMethods(BindingFlags.DeclaredOnly | BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic))
                .Where(x => (x.IsPublic || x.IsFamily || x.IsFamilyOrAssembly) && !x.IsSpecialName && x.Name.EndsWith("Async") && typeof(Task).IsAssignableFrom(x.ReturnType))
                .Select(x => new
                {
                    Name = x.DeclaringType.ToString() + "." + string.Join(" ", x.ToString().Split().Skip(1)),
                    Protected = x.DeclaringType.IsNestedFamily || x.DeclaringType.IsNestedFamORAssem || x.IsFamily || x.IsFamilyOrAssembly,
                    x.DeclaringType.Assembly
                })
                .OrderBy(x => x.Name).ToList();
            var asyncAssemblies = apis.Select(x => x.Assembly.GetName().Name).Distinct().OrderBy(x => x).ToList();
            Console.WriteLine("Found " + asyncAssemblies.Count + " assemblies:");
            foreach (var assembly in asyncAssemblies)
                Console.WriteLine("  " + assembly);
            foreach (var api in apis.Select(x => x.Name))
                Debug.WriteLine("  " + api);
            Console.WriteLine("Dumped " + apis.Count + " APIs to the debugger.");
            Console.ReadLine();
        }
    }
}