以不正确的格式保存下载的数据

Question

在我的Windows窗体应用程序中，每次重新打开我的软件并尝试下载附加数据意味着它以不正确的格式保存。 为什么会发生这样的事情。任何建议

保存数据的代码

 private void DownloadAttachment(DataGridViewCell dgvCell)
    {
        string fileName = Convert.ToString(dgvCell.Value);

        //Return if the cell is empty
        if (fileName == string.Empty)
            return;

        FileInfo fileInfo = new FileInfo(fileName);
        string fileExtension = fileInfo.Extension;

        byte[] byteData = null;

        //show save as dialog
        using (SaveFileDialog saveFileDialog1 = new SaveFileDialog())
        {
            //Set Save dialog properties
            saveFileDialog1.Filter = "Files (*" + fileExtension + ")|*" + fileExtension;
            saveFileDialog1.Title = "Save File as";
            saveFileDialog1.CheckPathExists = true;
            saveFileDialog1.FileName = fileName;

            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                string s = cncInfoDataGridView.Rows[dgvCell.RowIndex].Cells[1].Value.ToString();
                byteData = System.Text.Encoding.ASCII.GetBytes(s);
                File.WriteAllBytes(saveFileDialog1.FileName, byteData);
            }
        }
    }