Probably the simplest way to do it is to create a delegate and then BeginInvoke, followed by a wait at some time in the future, and an EndInvoke.
public bool Foo(){
Thread.Sleep(100000); // Do work
return true;
}
public SomeMethod()
{
var fooCaller = new Func<bool>(Foo);
// Call the method asynchronously
var asyncResult = fooCaller.BeginInvoke(null, null);
// Potentially do other work while the asynchronous method is executing.
// Finally, wait for result
asyncResult.AsyncWaitHandle.WaitOne();
bool fooResult = fooCaller.EndInvoke(asyncResult);
Console.WriteLine("Foo returned {0}", fooResult);
}