I´m using SQL Server 2005 and Visual Studio 2008, C#.

In the data source (the SQL Server data table) I use the DateTime format mm/dd/yyyy, however, in a forms overview (DataGridView) users would like to see a completely other format, with year, week number and day number of week (yyww,d) which is in string format. I´ve created an algorithm for the transformation between values (date to weekday), but can I populate the affected cells with yyww,d (string) instead of mm/dd/yyyy (DateTime)?

This is what I´ve been testing out, without success (and note, it´s on the last line the problem becomes obvious, as the cell value won´t accept a string on runtime - it still wants to be a DateTime...)

  private void DataGridViewQueryFindRequests_CellFormatting(
     object sender, DataGridViewCellFormattingEventArgs e)
  {
     string weekAndDay = "";

     DataGridViewCell cell = 
         DataGridViewQueryFindRequests.Rows[e.RowIndex].Cells[e.ColumnIndex];


     if (cell.ColumnIndex == 13 && cell.Value == null)
        mEmptyRow = true;

     if ((cell.ColumnIndex == 14 || cell.ColumnIndex == 15) && !mEmptyRow)
     {
        weekAndDay = ClassWeeksAndDates.dateToWeekNumber(Convert.ToDateTime(cell.Value));

        cell.ValueType = typeof(string);

        cell.Value = weekAndDay;
     }
   }