NPOI将Excel直接导出到前端，而无需将其保存在服务器上

Question

是否可以将excel文件（带有NPOI）直接写入浏览器，而无需先将其保存在服务器上。

我尝试在控制器中执行以下操作，但未成功：

public async Task<IActionResult> ExportExcel(){

    var fs = new MemoryStream();

    IWorkbook workbook;
    workbook = new XSSFWorkbook();
    ISheet excelSheet = workbook.CreateSheet("Test);

    IRow row = excelSheet.CreateRow(0);
    row.CreateCell(0).SetCellValue("ID");
    row.CreateCell(1).SetCellValue("Name");

    row = excelSheet.CreateRow(1);
    row.CreateCell(0).SetCellValue(1);
    row.CreateCell(1).SetCellValue("User 1");

    workbook.Write(fs);

    byte[] bytes = new byte[fs.Length];
    fs.Read(bytes, 0, (int)fs.Length);


    return File(bytes, "application/vnd.ms-excel", sampleType.Abbreviation+".xlsx"); 
}

执行上述方法时，总是出现以下错误：

ObjectDisposedException: Cannot access a closed Stream.

...
System.IO.MemoryStream.get_Length()
byte[] bytes = new byte[fs.Length];
...

还是他们另一个出色的nuget程序包来处理（读取和写入）excel文件而不在服务器上存储文件？

PS：我使用的是dotnet core 2.1 en nuget软件包：https://www.nuget.org/packages/NPOI/

Answer 1

1. 直接写到Response.Body。
2. 由于Excel被视为附件，因此我们还需要设置Response.Headers

为了使生活更轻松，我们可以首先创建一个扩展方法：

public static class IWorkBookExtensions {

    public static void WriteExcelToResponse(this IWorkbook book, HttpContext httpContext, string templateName)
    {
        var response = httpContext.Response;
        response.ContentType = "application/vnd.ms-excel";
        if (!string.IsNullOrEmpty(templateName))
        {
            var contentDisposition = new Microsoft.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
            contentDisposition.SetHttpFileName(templateName);
            response.Headers[HeaderNames.ContentDisposition] = contentDisposition.ToString();
        }
        book.Write(response.Body);
    }
}

现在我们可以直接导出excel文件：

public async Task ExportExcel(){

    IWorkbook workbook;
    workbook = new XSSFWorkbook();
    ISheet excelSheet = workbook.CreateSheet("Test");

    IRow row = excelSheet.CreateRow(0);
    row.CreateCell(0).SetCellValue("ID");
    row.CreateCell(1).SetCellValue("Name");

    row = excelSheet.CreateRow(1);
    row.CreateCell(0).SetCellValue(1);
    row.CreateCell(1).SetCellValue("User 1");

    workbook.WriteExcelToResponse(HttpContext,"test.xlsx");
}