C# グラフの値をCSVで保存する

using System.IO;   //Save
using System.Text; //Save

private void btnSave_Click(object sender, EventArgs e)
        {
            try
            {
                //ファイル書き込み形式（上書き）
                StreamWriter file = new StreamWriter(str_save_file, false, Encoding.UTF8);
                for (int i= 0; i < chart1.Series[str_ms_x].Points.Count; i++) {
                    file.WriteLine( chart1.Series[str_ms_x].Points[i].YValues[0] + "," + chart1.Series[str_ms_y].Points[i].YValues[0] );
                }
                file.Close();
                //セーブボタン使用不可
                btnSave.Enabled = false;
            }
            catch
            {
                
            }
        }