C# dll 事件执行 js 回调函数

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原作者: [db:作者] 来自: [db:来源] 收藏邀请

前言：

　　由于js 远程请求 XMLHttpRequest() 不支持多线程，所以用C# 写了个dll 多线程远程抓住供js调用。

最初代码为：

　　C#代码

/// <summary>
        /// 异步请求入口
        /// </summary>
        /// <param name="url">传入http地址 注意加http</param>
        /// <param name="timeoutStr">超时时间</param>
        public  void AsyncGet(string url, int timeoutStr)
        {
            try
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(new Uri(url));
                request.Timeout = timeoutStr;
                request.BeginGetResponse(new AsyncCallback(ReadCallBack), request);
            }
            catch (Exception) { }
        }

        /// <summary>
        /// 执行回调时候异步最终拿到值
        /// 正常获取反馈值，异常时候值为 timeout
        /// </summary>
        public  string returnContent { get; set; }

        /// <summary>
        /// 执行异步回调请求
        /// </summary>
        /// <param name="asynchronousResult"></param>
        private  void ReadCallBack(IAsyncResult asynchronousResult)
        {
            try
            {
                HttpWebRequest reqeust = (HttpWebRequest)asynchronousResult.AsyncState;
                HttpWebResponse response = (HttpWebResponse)reqeust.EndGetResponse(asynchronousResult);
                StreamReader readContent = new StreamReader(response.GetResponseStream());
                returnContent = readContent.ReadToEnd().ToString();
            }
            catch (Exception)
            {
                returnContent = "timeout";
            }
        }

js 代码：
　　

var Gtime = 5;
    function getUrl (turl) {
        if (Gtime==5) {
            comActiveX.AsyncGet(turl,Gtime);
        }
        if (Gtime>0 && comActiveX.returnContent==undefined) {
            setTimeout("getUrl('"+turl+"')",1000);
            alert(comActiveX.returnContent);
            Gtime -- ;
        }else{
            document.write( comActiveX.returnContent);
        }
    }

这里存在问题，js必须一直去询问dll 是否获取到数据，直到获取到数据才做下面处理，虽然其中可以做其他事情，但是这跟同步等待没有多大区别。

windows 经典编程有句话叫“don't call me , I will call you!” ，这就是事件的引入，那么这里可以不可以优化为，当有数据拿到以后自动通知js，js能不能注册一个回调函数。开始一通尝试，最终找到相关答案：

C# 加入以下代码：

    public delegate void EventHandler(string data);
    [Guid("9771B223-6188-4849-B292-C7D9D8173E49")]
    [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
    public interface ControlEvents
    {
        [DispId(0x60020000)]
        void eventsGet(string data);
    }

    /// <summary>
    /// 采集类
    /// </summary> 
    [ClassInterface(ClassInterfaceType.AutoDual), ComSourceInterfaces(typeof(ControlEvents))]
    public class CollectGood : UserControl
    {

        public event EventHandler eventsGet;

        private delegate void UpEventDelegate(string msg);

        public void Reback(string msg)
        {
            UpEventDelegate up = new UpEventDelegate(UpEvent);
            this.BeginInvoke(up, msg);
        }
        private void UpEvent(string msg)
        {
            if (eventsGet != null)
            {
                eventsGet(msg);
            }
        }

        #region httpWebRequest 异步请求Get方法
        /// <summary>
        /// 异步请求入口
        /// </summary>
        /// <param name="url">传入http地址 注意加http</param>
        /// <param name="timeoutStr">超时时间</param>
        public  void AsyncGet(string url, int timeoutStr)
        {
            try
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(new Uri(url));
                request.Timeout = timeoutStr;
                request.BeginGetResponse(new AsyncCallback(ReadCallBack), request);
            }
            catch (Exception) { }
        }

        /// <summary>
        /// 执行回调时候异步最终拿到值
        /// 正常获取反馈值，异常时候值为 timeout
        /// </summary>
        public  string returnContent { get; set; }

        /// <summary>
        /// 执行异步回调请求
        /// </summary>
        /// <param name="asynchronousResult"></param>
        private  void ReadCallBack(IAsyncResult asynchronousResult)
        {
            try
            {
                HttpWebRequest reqeust = (HttpWebRequest)asynchronousResult.AsyncState;
                HttpWebResponse response = (HttpWebResponse)reqeust.EndGetResponse(asynchronousResult);
                StreamReader readContent = new StreamReader(response.GetResponseStream());
                returnContent = readContent.ReadToEnd().ToString();
                Reback(returnContent);
            }
            catch (Exception)
            {
                returnContent = "timeout";
            }
        }
        #endregion

js部分：

<OBJECT >
</OBJECT> 
<SCRIPT type="text/javascript">
    //var comActiveX;
    try {
        //comActiveX = new ActiveXObject("HttpAsy.CollectGood");
    } catch (e) {
    //    alert("没有注册好");
    }
    comActiveX.attachEvent("eventsGet",function(msg){alert(msg)})
    
    comActiveX.AsyncGet("http:/www.baidu.com",5);

当运行后就会弹出百度源代码

这就实现了异步回调

https://files.cnblogs.com/echosong/http.rar 完整demo下载（先点reg.bat先注册dll）