public void ShowPictureOfString(string text)
        {
            byte[] buf = Convert.FromBase64String(text); 

            MemoryStream ms = new MemoryStream(buf);

            /*报错: 无效的参数*/
            Image img =Image.FromStream(ms);  //From Stream to a new Image
 
            this.pictureBox1.Image = img;

            ms.Close(); ms.Dispose();
}