OpenXML - Writing a date into Excel spreadsheet results in unreadable content

Question

I am using the following code to add a DateTime to a column in my spreadsheet:

var dt = DateTime.Now;
r.AppendChild(new Cell()
    {         


        

Answer 1

The following worked for us:

c.CellValue = new CellValue(datetimeValue).ToOADate().ToString());
c.DataType = CellValues.Number;
c.StyleIndex = StyleDate;

Set the DataType to CellValues.Number and then be sure to format the cell with the appropriate style index from the CellFormats. In our case we build a stylesheet within the worksheet, and StyleDate is an index into the CellFormats in the stylesheet.