Get distinct rows from datatable using Linq

var engData = (from dr in dtEng.AsEnumerable()
       where Convert.ToString(dr["job_number"]) == jobNumber
       && Convert.ToString(dr["period"]) == per.Periods
       && Convert.ToString(dr["office_short_name"]) == off.OfficeShortName
       select new
       {
        GroupCode = Convert.ToString(dr["group_code"]),
        GroupShortName = Convert.ToString(dr["group_short_name"]),
        CausalCountPeriod = (dr["casual_count_period"] == DBNull.Value || Convert.ToString(dr["casual_count_period"]) == "") ? Convert.ToInt32("0") : Convert.ToInt32(dr["casual_count_period"]),
        CausalCountToDate = (dr["casual_count_to_date"] == DBNull.Value || Convert.ToString(dr["casual_count_to_date"]) == "") ? Convert.ToInt32("0") : Convert.ToInt32(dr["casual_count_to_date"]),
        ReportingPeriod = Convert.ToString(dr["reporting_period"])
       }).Distinct();