class Program
{
    static void Main(string[] args)
    {
        Test test = new Test();
        test.TestAsync(ShowRes);
        Console.WriteLine("没有阻塞…");
        Console.ReadKey();
    }

    static void ShowRes(int sum)
    {
        Console.WriteLine($"总和：{sum}");
    }
}

public class Test
{
    public async void TestAsync(Action<int> callBack)
    {
        int sum = 0;
        await Task.Run(() =>
          {
              for (int i = 1; i <= 100; i++)
              {
                  sum += i;
                  Thread.Sleep(50);
              }
          });

        callBack(sum);
    }
}

输出：

没有阻塞…
总和：5050