private void btnBrowser_Click(object sender, EventArgs e)
        {
            OpenFileDialog fileDialog = new OpenFileDialog();
            fileDialog.Title = "选择文件";
            fileDialog.InitialDirectory = Application.StartupPath.ToString();
            fileDialog.Filter = "JPEG Files (*.jpg)|*.jpg|BMP Files (*.bmp)|*.bmp|PNG Files (*.png)|*.png";
            fileDialog.FilterIndex = 1;
            fileDialog.RestoreDirectory = true;

            if (fileDialog.ShowDialog() == DialogResult.OK)
            {
                FileInfo file = new FileInfo(fileDialog.FileName);
                txtImgUrl.Text = file.FullName;
            }
        }