Sorte a Datefield in ExcelSheet using C#

Hi Experts,

i try to sort an excelsheet based on a column polulated with date entries.

The problem seems to be, that the dates are handled as text.

What i want:
01.01.2013
02.01.2013
..
01.02.2013
02.02.2013

What i get:
01.01.2013
01.02.2013
..
02.01.2013
02.02.2013

The column (to be precise: The cells in the range to sort) is formated as a "Date" field in the worksheet.

Here is the Code i use:

Excel.Range range = oSheet.get_Range("A4:W" + iLastUsedRow, Type.Missing);

range.Sort(range.Columns[1, Type.Missing], Excel.XlSortOrder.xlAscending,Excel.XlYesNoGuess.xlNo,Type.Missing,Type.Missing,Excel.XlSortOrientation.xlSortColumns,Excel.XlSortMethod.xlPinYin,Excel.XlSortDataOption.xlSortTextAsNumbers);
 
System.Runtime.InteropServices.Marshal.ReleaseComObject(range);

Select allOpen in new window

Any help is greatly appreciated!
BR
Tom