How to call asynchronous method from synchronous method in C#?

Question

I have a public async void Foo() method that I want to call from synchronous method. So far all I have seen from MSDN documentation is calling async methods via

Answer 1

Microsoft built an AsyncHelper (internal) class to run Async as Sync. The source looks like:

internal static class AsyncHelper
{
    private static readonly TaskFactory _myTaskFactory = new 
      TaskFactory(CancellationToken.None, 
                  TaskCreationOptions.None, 
                  TaskContinuationOptions.None, 
                  TaskScheduler.Default);

    public static TResult RunSync(Func> func)
    {
        return AsyncHelper._myTaskFactory
          .StartNew>(func)
          .Unwrap()
          .GetAwaiter()
          .GetResult();
    }

    public static void RunSync(Func func)
    {
        AsyncHelper._myTaskFactory
          .StartNew(func)
          .Unwrap()
          .GetAwaiter()
          .GetResult();
    }
}

The Microsoft.AspNet.Identity base classes only have Async methods and in order to call them as Sync there are classes with extension methods that look like (example usage):

public static TUser FindById(this UserManager manager, TKey userId) where TUser : class, IUser where TKey : IEquatable
{
    if (manager == null)
    {
        throw new ArgumentNullException("manager");
    }
    return AsyncHelper.RunSync(() => manager.FindByIdAsync(userId));
}

public static bool IsInRole(this UserManager manager, TKey userId, string role) where TUser : class, IUser where TKey : IEquatable
{
    if (manager == null)
    {
        throw new ArgumentNullException("manager");
    }
    return AsyncHelper.RunSync(() => manager.IsInRoleAsync(userId, role));
}

For those concerned about the licensing terms of code, here is a link to very similar code (just adds support for culture on the thread) that has comments to indicate that it is MIT Licensed by Microsoft. https://github.com/aspnet/AspNetIdentity/blob/master/src/Microsoft.AspNet.Identity.Core/AsyncHelper.cs