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  strPostData += String.Format("&txt_Number={0}&txt_YZM={1}&__VIEWSTATE={2}&__EVENTVALIDATION={3}"
                                , this.UserName
                                , this.ExPwd
                                , this.__VIEWSTATE
                                , this.__EVENTVALIDATION
                                );
        strPostData = strPostData + "&IBt_ecall.x=8&IBt_ecall.y=12";
        System.Threading.Thread.Sleep(5000);        strHTML = GetHTML(strPostData,strPostData,Encoding.Default);
}public string GetHTML(string URL)
    {
        return GetHTML(URL, "", null);
    }
    public string GetHTML(string URL, System.Text.Encoding encoding)
    {
        return GetHTML(URL, "", encoding);
    }
    /// <summary>
    // 获取指定地址的html
    public string GetHTML(string URL, string PostData, System.Text.Encoding encoding)
    {
        string _Html = "";        try
        {
            Variant.Err = "";
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(URL));
            request.Accept = "image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms-excel, application/msword, application/x-shockwave-flash, */*";
            request.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Maxthon; .NET CLR 2.0.50727)";
            request.CookieContainer = this.ReqCookies;            if (encoding == null)
                encoding = Encoding.Default;            //设置cookie
            if (Variant.CurrentUser != null)
            {
                CookieCollection tmpCookies = Variant.CurrentUser.Cookies;                System.Uri uri = new Uri(URL);                foreach (System.Net.Cookie cookie in tmpCookies)
                {
                    cookie.Domain = uri.Host;
                    if (cookie.Value.Length != 0)
                    {
                        request.CookieContainer.Add(cookie);
                    }
                    else
                    {
                        //Console.WriteLine(cookie.ToString());
                    }
                }            }            //提交的数据
            if (PostData != null && PostData.Length > 0)
            {
                request.ContentType = "application/x-www-form-urlencoded";
                request.Method = "POST";                byte[] b = encoding.GetBytes(PostData);
                request.ContentLength = b.Length;
                using (System.IO.Stream sw = request.GetRequestStream())
                {
                    try
                    {                        sw.Write(b, 0, b.Length);
                    }
                    catch
                    {                        _Html = "";
                        return _Html;
                    }
                    finally
                    {
                        //if (sw != null) { sw.Close(); }
                    }
                }            }
            HttpWebResponse response = null;
            System.IO.StreamReader sr = null;
            try
            {
                response = (HttpWebResponse)request.GetResponse();
                this.Cookies.Add(response.Cookies);
                sr = new System.IO.StreamReader(response.GetResponseStream(), encoding);
                _Html = sr.ReadToEnd();
            }
            catch (WebException webex)
            {
                if (webex.Status == WebExceptionStatus.KeepAliveFailure)
                {
                    _Html = "";
                    Variant.Err = "KeepAliveFailure";
                    return _Html;
                }
                else
                {
                    _Html = "";
                    Variant.Err = webex.Message;
                    return _Html;
                }
            }
            catch (System.Exception ex)
            {
                _Html = "";
                Variant.Err = ex.Message;
                return _Html;
            }
            finally
            {
                if (sr != null) { sr.Close(); }
                if (response != null) { response.Close(); }
                response = null;
                request = null;
            }
            return _Html;
        }
        catch
        {
            return "";
        }
    }
在这里,我是要将想将参数提交到目的网站.请帮我看看哪里有问题?应该如何解决呀