常用异步延迟方法

    /// <summary>
    /// 定义与方法同签名的事件委托
    /// </summary>
    public delegate void AsyncEventHandler();

    /// <summary>
    /// 定义与方法同签名的回调方法委托
    /// </summary>
    /// <param name="ex">异常信息对象</param>
    public delegate void AsyncCallbackHandler(Exception ex);

    /// <summary>
    /// 异步调用引擎类
    /// </summary>
    public class AsyncCallEngine
    {
        /// <summary>
        /// 执行异步方法调用
        /// </summary>
        /// <param name="asyncMethod">异步执行的方法</param>
        /// <param name="callbackMethod">异步执行的方法执行后回调的方法</param>
        public static void Process(AsyncEventHandler asyncMethod, AsyncCallbackHandler callbackMethod)
        {
            try
            {
                //实例化委托并初赋值
                AsyncEventHandler acd = new AsyncEventHandler(asyncMethod);

                //实例化回调方法并订阅
                AsyncCallback acb = new AsyncCallback((ar) =>
                {
                    //从异步状态ar.AsyncState中，获取委托对象
                    acd = (AsyncEventHandler)ar.AsyncState;
                    Exception _ex = null;

                    try
                    {
                        //异步完成，执行回调方法
                        acd.EndInvoke(ar);
                    }
                    catch (Exception ex)
                    {
                        _ex = ex;
                    }

                    //调用回调函数
                    if (callbackMethod != null)
                    {
                        callbackMethod(_ex);
                    }
                });

                //异步开始
                IAsyncResult iar = acd.BeginInvoke(acb, acd);
            }
            catch (Exception ex)
            {
                //调用回调函数
                if (callbackMethod != null)
                {
                    callbackMethod(ex);
                }
            }
        }

        /// <summary>
        /// 执行异步方法调用
        /// </summary>
        /// <param name="asyncMethod">异步执行的方法</param>
        public static void Process(AsyncEventHandler asyncMethod)
        {
            Process(asyncMethod, null);
        }
    }