微信上传头像接口问题

[AK081]

http请求方式: POST/FORM
http://api.weixin.qq.com/customservice/kfaccount/uploadheadimg?access_token=ACCESS_TOKEN&kf_account=KFACCOUNT



string str = "{\"media\":[{\"filename\":\"" + fileName + "\",\"filelength\":\"" + data.Length + "\",\"content-type\":\"text/plain\"}]}";
string url = "http://api.weixin.qq.com/customservice/kfaccount/uploadheadimg?access_token=" + token + "&kf_account=" + kf_account + "";
try
{
// 设置参数
request = WebRequest.Create(url) as HttpWebRequest;
CookieContainer cookieContainer = new CookieContainer();
request.CookieContainer = cookieContainer;
request.AllowAutoRedirect = true;
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = data.Length;
outstream = request.GetRequestStream();
outstream.Write(data, 0, data.Length);
outstream.Close();
//发送请求并获取相应回应数据
response = request.GetResponse() as HttpWebResponse;
//直到request.GetResponse()程序才开始向目标网页发送Post请求
instream = response.GetResponseStream();
sr = new StreamReader(instream, encoding);
//返回结果网页（html）代码
string content = sr.ReadToEnd(); //返回结果
if (content.Contains("errcode\": 0") || content.Contains("errcode\":0"))
{
isok = 1;
}


试了好多种方法都是61451 参数错误(invalid parameter)，有哪位大神成功的，请分享下，急

[AK081]

多客服上传头像急急急

[小燕飞飞飞]

请问问题解决了吗