c#连接web接口上传图片

static void Main(string[] args){  
Uri host = new Uri("http://192.168.3.180:8089/api/tr-run/");
                    Encoding encoding = Encoding.Default;
                    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(host);
                    string base64 = getFileBase64(@"C:\Users\98468\Desktop\图片识别\5.png");
                    request.Method = "post";
                    request.ContentType = "application/x-www-form-urlencoded";
                    request.KeepAlive = true;
                    // 图片的base64编码
                    string str = "img=" + HttpUtility.UrlEncode(base64);
                    byte[] buffer = encoding.GetBytes(str);
                    request.ContentLength = buffer.Length;
                    request.GetRequestStream().Write(buffer, 0, buffer.Length);
                    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                    StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
                    string result = reader.ReadToEnd();
                    Console.WriteLine(result);
}
 public static  string getFileBase64(String fileName)
        {
            FileStream filestream = new FileStream(fileName, FileMode.Open);
            byte[] arr = new byte[filestream.Length];
            filestream.Read(arr, 0, (int)filestream.Length);
            string baser64 = Convert.ToBase64String(arr);
            filestream.Close();
            return baser64;
        }