How to add new row in gridview in asp.net(C#) when we allow paging true and page size="5"

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ASP.NET

I used in grid view when allowpaging="true" and pagesize="5" but i click in insert row button it show error,

i used this code

private void AddNewRow()
   {
       int rowIndex = 0;

       if (ViewState["CurrentTable"] != null)
       {
           DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
           DataRow drCurrentRow = null;
           if (dtCurrentTable.Rows.Count > 0)
           {
               for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
               {
                   TextBox txtEmpCode = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[1].FindControl("txtEmpCode");                  TextBox txtHours = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[2].FindControl("txtHours");
                   TextBox txtCode = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[3].FindControl("txtCode");

                   drCurrentRow = dtCurrentTable.NewRow();
                   drCurrentRow["RowNumber"] = i + 1;

                   dtCurrentTable.Rows[i - 1]["empl_code"] = txtEmpCode.Text;
                   dtCurrentTable.Rows[i - 1]["hours"] = txtHours.Text;
                   dtCurrentTable.Rows[i - 1]["awr_code"] = txtCode.Text.ToUpper();
                   rowIndex++;
               }
               dtCurrentTable.Rows.Add(drCurrentRow);
               ViewState["CurrentTable"] = dtCurrentTable;

               grvStudentDetails.DataSource = dtCurrentTable;
               grvStudentDetails.DataBind();



           }
       }
       else
       {
           Response.Write("ViewState is null");
       }
       SetPreviousData();
   }

the error is:-"

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

" this error come in bold line,

what when i am not using paging it will be correct.
what can i do please help me?