winform 中显示异步下载的图片

private void dataGridView1_RowsAdded(object sender, DataGridViewRowsAddedEventArgs e)
{
  ////利用 WebClient 来下载图片
  using (WebClient wc = new WebClient())
  {
    ////WebClient 下载完毕的响应事件绑定
    wc.DownloadDataCompleted += new DownloadDataCompletedEventHandler(wc_DownloadDataCompleted);

    ////开始异步下载，图片URL路径请根据实际情况自己去指定
    ////同时将DataGridView当前行的行号传递过去，用于指定图片显示的CELL
    wc.DownloadDataAsync(new Uri(this.dataGridView1.Rows[e.RowIndex].Cells[1].Value.ToString()),
      e.RowIndex);
  }
}


void wc_DownloadDataCompleted(object sender, DownloadDataCompletedEventArgs e)
{
  ////如果下载过程未发生错误，并且未被中途取消
  if (e.Error == null && !e.Cancelled)
  {
    ////将图片显示于对应的指定单元格， e.UserState 就是传入的 e.RowIndex
    ////e.Result 就是下载结果
    this.dataGridView1.Rows[(int)e.UserState].Cells["src"].Value = e.Result;
    // this.dataGridView1.Rows[(int)e.UserState].Cells["test"].Value = GetImage("1");
  }
}