OpenXML - Cell.DateType 为 null

使用OpenXML编程时，有时我们需要设置单元格的日期格式。在OpenXML中，可以使用Cell.DataType属性来指定单元格的数据类型，包括日期类型。但是，在某些情况下，我们可能无法直接设置Cell.DataType为日期类型，即Cell.DataType属性为null。那么我们该如何处理这种情况呢？

csharp
// 创建一个新的Excel文档
using (SpreadsheetDocument document = SpreadsheetDocument.Create("Sample.xlsx", SpreadsheetDocumentType.Workbook))
{
    // 添加一个工作表
    WorkbookPart workbookPart = document.AddWorkbookPart();
    workbookPart.Workbook = new Workbook();
    WorksheetPart worksheetPart = workbookPart.AddNewPart();
    worksheetPart.Worksheet = new Worksheet(new SheetData());
    Sheets sheets = workbookPart.Workbook.AppendChild(new Sheets());
    Sheet sheet = new Sheet() { Id = workbookPart.GetIdOfPart(worksheetPart), SheetId = 1, Name = "Sheet1" };
    sheets.Append(sheet);
    // 添加数据到单元格
    SheetData sheetData = worksheetPart.Worksheet.GetFirstChild();
    Row row = new Row();
    sheetData.Append(row);
    Cell cell = new Cell() { CellReference = "A1" };
    row.Append(cell);
    // 设置单元格的值为日期的字符串表示
    cell.CellValue = new CellValue(DateTime.Now.ToString("yyyy-MM-dd"));
    cell.DataType = new EnumValue(CellValues.String);
    // 保存文档
    workbookPart.Workbook.Save();
}
Console.WriteLine("Excel文档创建成功！");

csharp
using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Spreadsheet;
using System;
namespace OpenXMLDateHandling
{
    class Program
    {
        static void Main(string[] args)
        {
            // 创建一个新的Excel文档
            using (SpreadsheetDocument document = SpreadsheetDocument.Create("Sample.xlsx", SpreadsheetDocumentType.Workbook))
            {
                // 添加一个工作表
                WorkbookPart workbookPart = document.AddWorkbookPart();
                workbookPart.Workbook = new Workbook();
                WorksheetPart worksheetPart = workbookPart.AddNewPart();
                worksheetPart.Worksheet = new Worksheet(new SheetData());
                Sheets sheets = workbookPart.Workbook.AppendChild(new Sheets());
                Sheet sheet = new Sheet() { Id = workbookPart.GetIdOfPart(worksheetPart), SheetId = 1, Name = "Sheet1" };
                sheets.Append(sheet);
                // 添加数据到单元格
                SheetData sheetData = worksheetPart.Worksheet.GetFirstChild();
                Row row = new Row();
                sheetData.Append(row);
                Cell cell = new Cell() { CellReference = "A1" };
                row.Append(cell);
                // 设置单元格的值为日期的字符串表示
                cell.CellValue = new CellValue(DateTime.Now.ToString("yyyy-MM-dd"));
                cell.DataType = new EnumValue(CellValues.String);
                // 保存文档
                workbookPart.Workbook.Save();
            }
            Console.WriteLine("Excel文档创建成功！");
        }
    }
}