像往常一样迟到，但我必须发布一个答案，因为之前的所有答案都是完全错误的，除了 Oleh 被否决的答案，遗憾的是不完整。
由于问题与 Excel 有关，最简单的做法是创建一个包含所需数据和样式的 Excel 电子表格，然后将其作为部分打开并查看原始 XML。
将日期 01/01/2015 添加到单元格 A1 中会产生以下结果：
<row r="1">
<c r="A1" s="0">
<v>42005</v>
</c>
</row>
请注意，type 属性在此处不是。但是，有一个样式属性引用了以下样式：
<xf numFmtId="14" fontId="0" fillId="0" borderId="0" xfId="0" applyNumberFormat="1" />
这是您必须添加的最基本样式。
所以生成上面的代码：
- 您需要按如下方式创建样式：
var CellFormats = new CellFormats();
CellFormats.Append(new CellFormat()
{
BorderId = 0,
FillId = 0,
FontId = 0,
NumberFormatId = 14,
FormatId = 0,
ApplyNumberFormat = true
});
CellFormats.Count = (uint)CellFormats.ChildElements.Count;
var StyleSheet = new Stylesheet();
StyleSheet.Append(CellFormats);
NumberFormatId = 14指的是内置格式mm-dd-yy，这里是list of some other formats。
不幸的是，添加 just 上述样式似乎还不够，如果这样做实际上会导致 Excel 崩溃。注意BorderId、FillId、FontId需要对应样式表中的一个项目，这意味着你需要提供它们。完整代码清单中的 GetStyleSheet() 方法提供了 Excel 正常工作所需的最低默认样式表。
- 并添加如下单元格：
SheetData.AppendChild(new Row(
new Cell()
{
// CellValue is set to OADate because that's what Excel expects.
CellValue = new CellValue(date.ToOADate().ToString(CultureInfo.InvariantCulture)),
// Style index set to style (0 based).
StyleIndex = 0
}));
注意：Office 2010 和 2013 可以以不同的方式处理日期，但默认情况下似乎不会。
它们支持 ISO 8601 格式的日期，即yyyy-MM-ddTHH:mm:ss，恰好这也是可排序的标准格式（“s”），因此您可以这样做：
SheetData.AppendChild(new Row(
new Cell()
{
CellValue = new CellValue(date.ToString("s")),
// This time we do add the DataType attribute but ONLY for Office 2010+.
DataType = CellValues.Date
StyleIndex = 1
}));
结果：
<row>
<c s="0" t="d">
<v>2015-08-05T11:13:57</v>
</c>
</row>
完整的代码清单
以下是添加日期格式单元格所需的最少代码示例。
private static void TestExcel()
{
using (var Spreadsheet = SpreadsheetDocument.Create("C:\\Example.xlsx", SpreadsheetDocumentType.Workbook))
{
// Create workbook.
var WorkbookPart = Spreadsheet.AddWorkbookPart();
var Workbook = WorkbookPart.Workbook = new Workbook();
// Add Stylesheet.
var WorkbookStylesPart = WorkbookPart.AddNewPart<WorkbookStylesPart>();
WorkbookStylesPart.Stylesheet = GetStylesheet();
WorkbookStylesPart.Stylesheet.Save();
// Create worksheet.
var WorksheetPart = Spreadsheet.WorkbookPart.AddNewPart<WorksheetPart>();
var Worksheet = WorksheetPart.Worksheet = new Worksheet();
// Add data to worksheet.
var SheetData = Worksheet.AppendChild(new SheetData());
SheetData.AppendChild(new Row(
new Cell() { CellValue = new CellValue(DateTime.Today.ToOADate().ToString(CultureInfo.InvariantCulture)), StyleIndex = 1 },
// Only works for Office 2010+.
new Cell() { CellValue = new CellValue(DateTime.Today.ToString("s")), DataType = CellValues.Date, StyleIndex = 1 }));
// Link worksheet to workbook.
var Sheets = Workbook.AppendChild(new Sheets());
Sheets.AppendChild(new Sheet()
{
Id = WorkbookPart.GetIdOfPart(WorksheetPart),
SheetId = (uint)(Sheets.Count() + 1),
Name = "Example"
});
Workbook.Save();
}
}
private static Stylesheet GetStylesheet()
{
var StyleSheet = new Stylesheet();
// Create "fonts" node.
var Fonts = new Fonts();
Fonts.Append(new Font()
{
FontName = new FontName() { Val = "Calibri" },
FontSize = new FontSize() { Val = 11 },
FontFamilyNumbering = new FontFamilyNumbering() { Val = 2 },
});
Fonts.Count = (uint)Fonts.ChildElements.Count;
// Create "fills" node.
var Fills = new Fills();
Fills.Append(new Fill()
{
PatternFill = new PatternFill() { PatternType = PatternValues.None }
});
Fills.Append(new Fill()
{
PatternFill = new PatternFill() { PatternType = PatternValues.Gray125 }
});
Fills.Count = (uint)Fills.ChildElements.Count;
// Create "borders" node.
var Borders = new Borders();
Borders.Append(new Border()
{
LeftBorder = new LeftBorder(),
RightBorder = new RightBorder(),
TopBorder = new TopBorder(),
BottomBorder = new BottomBorder(),
DiagonalBorder = new DiagonalBorder()
});
Borders.Count = (uint)Borders.ChildElements.Count;
// Create "cellStyleXfs" node.
var CellStyleFormats = new CellStyleFormats();
CellStyleFormats.Append(new CellFormat()
{
NumberFormatId = 0,
FontId = 0,
FillId = 0,
BorderId = 0
});
CellStyleFormats.Count = (uint)CellStyleFormats.ChildElements.Count;
// Create "cellXfs" node.
var CellFormats = new CellFormats();
// A default style that works for everything but DateTime
CellFormats.Append(new CellFormat()
{
BorderId = 0,
FillId = 0,
FontId = 0,
NumberFormatId = 0,
FormatId = 0,
ApplyNumberFormat = true
});
// A style that works for DateTime (just the date)
CellFormats.Append(new CellFormat()
{
BorderId = 0,
FillId = 0,
FontId = 0,
NumberFormatId = 14, // or 22 to include the time
FormatId = 0,
ApplyNumberFormat = true
});
CellFormats.Count = (uint)CellFormats.ChildElements.Count;
// Create "cellStyles" node.
var CellStyles = new CellStyles();
CellStyles.Append(new CellStyle()
{
Name = "Normal",
FormatId = 0,
BuiltinId = 0
});
CellStyles.Count = (uint)CellStyles.ChildElements.Count;
// Append all nodes in order.
StyleSheet.Append(Fonts);
StyleSheet.Append(Fills);
StyleSheet.Append(Borders);
StyleSheet.Append(CellStyleFormats);
StyleSheet.Append(CellFormats);
StyleSheet.Append(CellStyles);
return StyleSheet;
}