C#中将中文字符转换成url编码

Encoding gb2312 = Encoding.GetEncoding("gb2312");
Encoding utf8 = Encoding.UTF8;
//首先用utf-8进行解码
string key = HttpUtility.UrlDecode(oStr, utf8);
// 将已经解码的字符再次进行编码.
string encode = HttpUtility.UrlEncode(key, utf8).ToLower();