get distict column with value from datatable

 DataTable dtParameter = (DataTable)((ListBox)chkParameter).DataSource;
                        var distinctNames = (from row in dtGridSeries.AsEnumerable()
                                             select row.Field<string>("Parameter Type")).Distinct();
                        List<string> lstSelectedParamList = distinctNames.ToList();


                              or

 //----------Get Distinct Record only
       //  DataTable dtUnique = dtGridSeries.DefaultView.ToTable(true, "Parameter Type");