C＃ - 无法从longbinary数据类型列的sybase数据库（SQL Anywhere）读取数据

Question

以下是我的代码：

        string ConnectionString = "Provider=ASAProv;Server Name=MyServer;Initial Catalog=MyCatalog;User id=MyUserID;Password=MyPassword;";


        DataTable dt = returnTable();
        lblTest.Text = Convert.ToString(dt.Rows[0]["Image"]);
        byte[] data = (byte[])dt.Rows[0]["Image"];
        MemoryStream ms = new MemoryStream(data);
        System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
        img.Save(System.IO.Path.GetTempPath() + "\\myImage.Jpeg");

byte []数据返回System.Byte []类型，长度为0