.Net AsyncStateMachine自定义实现行为

using System;
using System.Threading.Tasks;

public class CustomAsyncStateMachine : IAsyncStateMachine
{
    private int _state;
    private TaskAwaiter<int> _awaiter;

    public void MoveNext()
    {
        int result;
        try
        {
            switch (_state)
            {
                case 0:
                    Console.WriteLine("Starting async operation...");
                    _awaiter = Task.Delay(1000).GetAwaiter();
                    _state = 1;
                    return;

                case 1:
                    result = _awaiter.GetResult();
                    Console.WriteLine("Async operation completed.");
                    break;

                default:
                    throw new InvalidOperationException();
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
            throw;
        }
    }

    public void SetStateMachine(IAsyncStateMachine stateMachine)
    {
        // This method is required by the interface but is not used in this example.
    }
}

public class Program
{
    public static async Task Main(string[] args)
    {
        var stateMachine = new CustomAsyncStateMachine();
        stateMachine.MoveNext();
    }
}