How to make correct date format when writing data to Excel

Question

Iam exporting a DataTable to an Excel-file using office interop. The problem is, that Excel does not recognize dates as such, but instead it displays numbers. In another case I pass a string which it then recognizes as a date. In both cases the data is messed up.

I tried NumberFormat @ which is supposed to store the cell in text format, but it didn't work either.

Application app = new Application(); app.Visible = false; app.ScreenUpdating = false; app.DisplayAlerts = false; app.EnableAnimations = false; app.EnableAutoComplete = false; app.EnableSound = false; app.EnableTipWizard = false; app.ErrorCheckingOptions.BackgroundChecking = false;   Workbook wb = app.Workbooks.Add(XlWBATemplate.xlWBATWorksheet); Worksheet ws = (Worksheet)wb.Worksheets[1];  for (int j = 0; j < dt.Rows.Count; j++) {     for (int i = 0; i < dt.Columns.Count; i++)     {         Range rng = ws.Cells[j+2, i+1]as Range;         rng.Value2 = dt.Rows[j][i].ToString();         rng.NumberFormat = "@";     }    }             wb.SaveAs(filename, Missing.Value, Missing.Value, Missing.Value, Missing.Value,        Missing.Value, XlSaveAsAccessMode.xlExclusive, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value);  wb.Close(false, Missing.Value, Missing.Value);              app.Workbooks.Close(); app.Application.Quit(); app.Quit();     System.Runtime.InteropServices.Marshal.ReleaseComObject(ws); System.Runtime.InteropServices.Marshal.ReleaseComObject(wb); System.Runtime.InteropServices.Marshal.ReleaseComObject(app); ws = null; wb = null; app = null; GC.Collect(); 

Why doesn't my NumberFormat @ work? Shouldn't Textformat display everything the same as I put it in?

Answer 1

Did you try formatting the entire column as a date column? Something like this:

Range rg = (Excel.Range)worksheetobject.Cells[1,1]; rg.EntireColumn.NumberFormat = "MM/DD/YYYY"; 

The other thing you could try would be putting a single tick before the string expression before loading the text into the Excel cell (not sure if that matters or not, but it works when typing text directly into a cell).

Answer 2

Try using

DateTime.ToOADate() 

And putting that as a double in the cell. There could be issues with Excel on Mac Systems (it uses a different datetime-->double conversion), but it should work well for most cases.

Hope this helps.