FileStream fsInfo = new FileStream("d:/试题.txt", FileMode.OpenOrCreate, FileAccess.Write);
            StreamWriter swInfo = new StreamWriter(fsInfo, Encoding.UTF8);
            swInfo.Flush();
            swInfo.BaseStream.Seek(0, SeekOrigin.Begin);
            foreach (DataGridViewRow row in this.dataGridView1.Rows)
            {
                string str = String.Empty;
                foreach (DataGridViewCell col in row.Cells)
                {
                    str += col.Value + "   ";

                }
                str += swInfo.NewLine;
                swInfo.Write(str);
以上代码是将dataGridView1中的全部内容写入TXT文档，我在dataGridView1中已经加入可供选择的按钮，请问如何把自己的选择内容写入TXT文档中，谢谢！！！