问导出.Net时损坏的Excel/电子表格文件

EN

[Route("api/tools")]
public class ImportExportController : Controller
{
    private readonly IHostingEnvironment _hostingEnvironment;

    public ImportExportController(IHostingEnvironment hostingEnvironment)
    {
        this._hostingEnvironment = hostingEnvironment;
    }
    [HttpGet]
    [Route("export")]
    public async Task<IActionResult> Export()
    {
        string sWebRootFolder = this._hostingEnvironment.WebRootPath;
        string sFileName = @"demo.xls";
        string URL = string.Format("{0}://{1}/{2}", this.Request.Scheme, this.Request.Host, sFileName);
        FileInfo filePath = new FileInfo(Path.Combine(sWebRootFolder, sFileName));
        var memory = new MemoryStream();

        SpreadsheetManager.SpreadsheetGenerator(filePath.FullName, sFileName);

        using (var stream = new FileStream(Path.Combine(sWebRootFolder, sFileName), FileMode.Open))
        {
            await stream.CopyToAsync(memory);
        }

        memory.Position = 0;

        return this.File(memory, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", sFileName);
    }
}

public static class SpreadsheetManager
{
    public static void SpreadsheetGenerator(string filePath, string fileName)
    {
        if (File.Exists(filePath))
        {
            File.Delete(filePath);
        }

        SpreadsheetDocument document = SpreadsheetDocument.Create(filePath, SpreadsheetDocumentType.Workbook);

        using (document)
        {
           WorkbookPart workbookPart = document.AddWorkbookPart();
            workbookPart.Workbook = new Workbook();

            WorksheetPart worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
            worksheetPart.Worksheet = new Worksheet(new SheetData());

            Sheets sheets = workbookPart.Workbook.AppendChild(new Sheets());

            Sheet sheet = new Sheet() { Id = workbookPart.GetIdOfPart(worksheetPart), SheetId = 1, Name = "Test Sheet" };

            sheets.Append(sheet);

            workbookPart.Workbook.Save();
            
        }
    }
}