Open Xml 写入日期类型

if (rIndex == 1)
{
cell.CellValue = new CellValue(item.ToString());
}
else if (rIndex == 2)
{
cell.CellValue = new CellValue(((DateTime)item).ToOADate().ToString());
cell.StyleIndex = 1;
}
else
{
int index = InsertSharedStringItem(item.ToString(), m_SharedStringTablePart);
cell.CellValue = new CellValue(index.ToString());
cell.DataType = new EnumValue<CellValues>(CellValues.SharedString);
}

static Stylesheet CreateStylesheet()
{
Stylesheet stylesheet1 = new Stylesheet();

Fonts fonts1 = new Fonts() { Count = (UInt32Value)1U, KnownFonts = true };
Font font1 = new Font();
fonts1.Append(font1);
Fills fills1 = new Fills() { Count = (UInt32Value)1U };
Fill fill1 = new Fill();
fills1.Append(fill1);
Borders borders1 = new Borders() { Count = (UInt32Value)1U };
Border border1 = new Border();
borders1.Append(border1);

CellFormats cellFormats1 = new CellFormats() { Count = (UInt32Value)2U };
CellFormat cellFormat1 = new CellFormat() ;
CellFormat cellFormat2 = new CellFormat()
{
NumberFormatId = (UInt32Value)22U,
ApplyNumberFormat = true
};
cellFormats1.Append(cellFormat1);
cellFormats1.Append(cellFormat2);

stylesheet1.Append(fonts1);
stylesheet1.Append(fills1);
stylesheet1.Append(borders1);
stylesheet1.Append(cellFormats1);

return stylesheet1;
}