方法1：

        System.Net.WebClient WebClientObj = new System.Net.WebClient();
        System.Collections.Specialized.NameValueCollection PostVars = new System.Collections.Specialized.NameValueCollection();
        PostVars.Add("A1", "xxx");
        PostVars.Add("A2", "0");
        PostVars.Add("A3", "000");
 


        byte[] byRemoteInfo = WebClientObj.UploadValues("https://www.xxx.com", "POST", PostVars);
        string sRemoteInfo = System.Text.Encoding.Default.GetString(byRemoteInfo);
        Response.Write(sRemoteInfo);

方法2：

string url = "https://www.xxx.com/api/";
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
        
 
string postdata = "key=djfkdjkf";
        byte[] requestBytes = System.Text.Encoding.UTF8.GetBytes(postdata);
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
        req.ContentLength = requestBytes.Length;
        req.Referer = "https://www.xxx.com";
        Stream requestStream 
 
= req.GetRequestStream();
        requestStream.Write(requestBytes, 0, requestBytes.Length);
        requestStream.Close();
        HttpWebResponse res = (HttpWebResponse)req.GetResponse();
        StreamReader sr = new StreamReader(res.GetResponseStream(), System.Text.Encoding.UTF8);
        string backstr = sr.ReadToEnd();
        Response.Write(backstr); 
        sr.Close(); 
        res.Close();

Asp.Net模擬post提交數據方法