1. private string HttpPostNew(string Url,string postDataStr)   
2. {  
3.     //string post_string = Encoding.UTF8.GetString(Encoding.UTF8.GetBytes(postDataStr));  
4.     byte[] postBytes = Encoding.GetEncoding("utf-8").GetBytes(postDataStr);  
5.     HttpWebRequest request = WebRequest.Create(Url) as HttpWebRequest;//(HttpWebRequest)WebRequest.Create(Url);  
6.     request.Method = "POST";  
7.     //request.ContentType = "application/x-www-form-urlencoded";  
8.     request.ContentType = "application/json";  
9.       
10.     request.ContentLength = postBytes.Length;//Encoding.UTF8.GetByteCount(post_string);  
11.     // request.CookieContainer = cookie;  
12.   
13.     Stream myRequestStream = request.GetRequestStream();  
14.     //StreamWriter myStreamWriter = new StreamWriter(myRequestStream, Encoding.GetEncoding("utf-8"));             
15.     //myStreamWriter.Write(post_string);  
16.     //myStreamWriter.Close();  
17.   
18.   
19.     myRequestStream.Write(postBytes, 0, postBytes.Length);  
20.     myRequestStream.Close();  
21.   
22.     HttpWebResponse response = (HttpWebResponse)request.GetResponse();  
23.   
24.     //response.Cookies = cookie.GetCookies(response.ResponseUri);  
25.     Stream myResponseStream = response.GetResponseStream();  
26.     StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));  
27.     string retString = myStreamReader.ReadToEnd();  
28.     myStreamReader.Close();  
29.     myResponseStream.Close();  
30.   
31.     return retString;  
32. }  

以下函数不能解决中文上传问题，如果上传的数据里有中文，写入的时候就会出错：

1. private string HttpPost(string Url, string postDataStr)  
2. {  
3.     HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);  
4.     request.Method = "POST";  
5.     request.ContentType = "application/json";  
6.     request.ContentLength = Encoding.UTF8.GetByteCount(postDataStr);  
7.     Stream myRequestStream = request.GetRequestStream();  
8.     StreamWriter myStreamWriter = new StreamWriter(myRequestStream, Encoding.GetEncoding("gb2312"));  
9.     myStreamWriter.Write(postDataStr);  
10.     myStreamWriter.Close();  
11.     HttpWebResponse response = (HttpWebResponse)request.GetResponse();  
12.     Stream myResponseStream = response.GetResponseStream();  
13.     StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));  
14.     string retString = myStreamReader.ReadToEnd();  
15.     myStreamReader.Close();  
16.     myResponseStream.Close();  
17.     return retString;  
18. }  

1. private string HttpPostNew(string Url,string postDataStr)   
2. {  
3.     //string post_string = Encoding.UTF8.GetString(Encoding.UTF8.GetBytes(postDataStr));  
4.     byte[] postBytes = Encoding.GetEncoding("utf-8").GetBytes(postDataStr);  
5.     HttpWebRequest request = WebRequest.Create(Url) as HttpWebRequest;//(HttpWebRequest)WebRequest.Create(Url);  
6.     request.Method = "POST";  
7.     //request.ContentType = "application/x-www-form-urlencoded";  
8.     request.ContentType = "application/json";  
9.       
10.     request.ContentLength = postBytes.Length;//Encoding.UTF8.GetByteCount(post_string);  
11.     // request.CookieContainer = cookie;  
12.   
13.     Stream myRequestStream = request.GetRequestStream();  
14.     //StreamWriter myStreamWriter = new StreamWriter(myRequestStream, Encoding.GetEncoding("utf-8"));             
15.     //myStreamWriter.Write(post_string);  
16.     //myStreamWriter.Close();  
17.   
18.   
19.     myRequestStream.Write(postBytes, 0, postBytes.Length);  
20.     myRequestStream.Close();  
21.   
22.     HttpWebResponse response = (HttpWebResponse)request.GetResponse();  
23.   
24.     //response.Cookies = cookie.GetCookies(response.ResponseUri);  
25.     Stream myResponseStream = response.GetResponseStream();  
26.     StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));  
27.     string retString = myStreamReader.ReadToEnd();  
28.     myStreamReader.Close();  
29.     myResponseStream.Close();  
30.   
31.     return retString;  
32. }