How to save datatable as a .csv file?

public void ConvertDatatableToCSV(Datatable user_defined_datatable )
{
      
private System.Windows.Forms.SaveFileDialog user_save_dialog_box;         
 try
                {
                    user_save_dialog_box.Filter = "CSV Files | *.csv";
                    if (user_save_dialog_box.ShowDialog() != System.Windows.Forms.DialogResult.Cancel)
                    {
                        user_defined_file_name = user_save_dialog_box.FileName;                     

                        Microsoft.Office.Interop.Excel.Application excelApplication = new Microsoft.Office.Interop.Excel.Application();
                        excelApplication.Visible = false;

                        Microsoft.Office.Interop.Excel.Workbook workbook = excelApplication.Workbooks.Add(Microsoft.Office.Interop.Excel.XlWBATemplate.xlWBATWorksheet);
                        Microsoft.Office.Interop.Excel.Worksheet worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.ActiveSheet;

                        // This is used for Header.   
                        for (int i = 0; i < user_defined_datatable.Columns.Count; i++)
                        {
                            worksheet.Cells[1, i + 1] = user_defined_datatable.Columns[i].ColumnName;
                        }

                        // This is used for contents   
                        for (int i = 0; i < user_defined_datatable.Rows.Count; i++)
                        {
                            for (int j = 0; j < user_defined_datatable.Columns.Count; j++)
                           {
                                worksheet.Cells[i + 2, j + 1] = user_defined_datatable.Rows[i][j].ToString();
                            }
                        }
                      
                        workbook.SaveAs(user_defined_file_name, Microsoft.Office.Interop.Excel.XlFileFormat.xlWorkbookNormal, Type.Missing, Type.Missing, false, false, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlShared, false, false, Type.Missing, Type.Missing, Type.Missing);
                        workbook.Close(true, Type.Missing, Type.Missing);
                        excelApplication.Quit();
                    }

                }
                catch
                {
                    MessageBox.Show("Save Error", "Application_name", System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Error);
                }
            }