Coumn batchid does not belong to table table1

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C#5.0

Page load code as follows

PkgDates.Columns.Add("Cmn_minor_code", typeof(string));
            PkgDates.Columns.Add("BatchID", typeof(string));
            PkgDates.Columns.Add("Disp_Course", typeof(string));
            PkgDates.Columns.Add("Start_date", typeof(DateTime));
            PkgDates.Columns.Add("End_date", typeof(DateTime));
            PkgRows = PkgDates.NewRow();

            if (this.DdlPKGCode.Text != "")
            {
                return;
            }
            ViewState["table"] = PkgDates;

I have one submit button.Submit button code as follows

PkgRows = PkgDates.NewRow();
       PkgRows["Cmn_minor_code"] = this.DDLPKGMinorCode.Text.ToString().TrimEnd();
       PkgRows["BatchID"] = this.LstPKGCrsDate.SelectedValue.ToString().TrimEnd();

      PkgRows["Start_date"] = Dt_Batches.Rows[LstPKGCrsDate.SelectedIndex][2];
      PkgRows["End_date"] = Dt_Batches.Rows[LstPKGCrsDate.SelectedIndex][3];
  PkgRows["Disp_Course"] = this.DDLPKGMinorCode.Text.ToString() + " - " + StrDate;

       this.PkgDates.Rows.Add(PkgRows);
       ViewState["table"] = PkgDates;

       ViewState["AdCrsCount"] = PkgDates.Rows.Count;

When i run and click the submit button shows error as follows

Column 'BatchID' does not belong to table Table1.

please help me from my above what is the mistake i made.