Problème réponse WebClient

public void uploadImage()
{
            string api = "http://www.noelshack.com/api.php";
            string fileName = "file.jpg";
            WebClient wc = new WebClient();
            byte[] responseArray = wc.UploadFile(api, fileName);
            // Decode and display the response.
            MessageBox.Show(System.Text.Encoding.ASCII.GetString(responseArray), responseArray.Length.ToString(), MessageBoxButtons.OK, MessageBoxIcon.Information);
}