how do I zip multiple files using GZipStream in c#

I have created multiple csv files using datatable and want to zip all those file into one single zip file. Which is i'm doing all at dynamically.
I tried following code
List<string> filestream = GenerateCSVfiles(dataSets); //Generate CSV files public List<string> GenerateCSVfiles(List<DataSet> dataSets) { List<string> filestream = new List<string>(); StringBuilder result = null; foreach (DataSet dataSet in dataSets) { result = new StringBuilder(); System.Data.DataTable dataTable = dataSet.Tables[0]; foreach (DataColumn colm in dataTable.Columns) { result.Append(colm.ColumnName+","); } result.Append("\n"); //create csv file foreach (DataRow row in dataTabl ...