ASP.NET Core return excel file (xlsx) directly in one call to the server (on the fly)?

Question

I have found solution for generating excel file (xlsx) on the server.On first call it deletes the file demo.xlsx if it exists and generates new demo.xlsx.

First call http://localhost:8000/api/importexport/export

it generates excel file (xlsx) and sends url for download

Second call http://localhost:8000/demo.xlsx

downloads the file. In Startup class in Configure method you must add app.UseStaticFiles();

Here is the link for solution http://www.talkingdotnet.com/import-export-xlsx-asp-net-core/

The problem with this solution is that I have two calls to server. I want in one call http://localhost:8000/api/importexport/export to directly download excel file (xlsx). I heard that its possible to download excel file (xlsx) in one call without creating file on the server(on the fly). I would be glad to see better solution in one call to the server.

Answer 1

It's easy, just return File (like of View or Redirect, but File):

public async Task<ActionResult> Index()
{
    var fileMemoryStream = await GenerateReportAndWriteToMemoryStream(...);
    return File(
        fileMemoryStream, 
        "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", 
        "report.xlsx");
}

This method is part of ControllerBase and has several signatures, choose best that fit your needs:

File(byte[] fileContents, string contentType)
File(Stream fileStream, string contentType)
File(string virtualPath, string contentType)
File(string virtualPath, string contentType, string fileDownloadName)
File(byte[] fileContents, string contentType, string fileDownloadName)
File(Stream fileStream, string contentType, string fileDownloadName)

Answer 2

Here is my solution

   private readonly IHostingEnvironment _hostingEnvironment;

    public ImportExportController(IHostingEnvironment hostingEnvironment)
    {
        _hostingEnvironment = hostingEnvironment;
    }

    [HttpGet]
    [Route("Export")]
    public IActionResult Export()
    {
        string sWebRootFolder = _hostingEnvironment.WebRootPath;
        string sFileName = @"demo.xlsx";
        string URL = string.Format("{0}://{1}/{2}", Request.Scheme, Request.Host, sFileName);
        FileInfo file = new FileInfo(Path.Combine(sWebRootFolder, sFileName));
        if (file.Exists)
        {
            file.Delete();
            file = new FileInfo(Path.Combine(sWebRootFolder, sFileName));
        }
        using (ExcelPackage package = new ExcelPackage(file))
        {
            // add a new worksheet to the empty workbook
            ExcelWorksheet worksheet = package.Workbook.Worksheets.Add("Employee");
            //First add the headers
            worksheet.Cells[1, 1].Value = "ID";
            worksheet.Cells[1, 2].Value = "Name";
            worksheet.Cells[1, 3].Value = "Gender";
            worksheet.Cells[1, 4].Value = "Salary (in $)";

            //Add values
            worksheet.Cells["A2"].Value = 1000;
            worksheet.Cells["B2"].Value = "Jon";
            worksheet.Cells["C2"].Value = "M";
            worksheet.Cells["D2"].Value = 5000;

            worksheet.Cells["A3"].Value = 1001;
            worksheet.Cells["B3"].Value = "Graham";
            worksheet.Cells["C3"].Value = "M";
            worksheet.Cells["D3"].Value = 10000;

            worksheet.Cells["A4"].Value = 1002;
            worksheet.Cells["B4"].Value = "Jenny";
            worksheet.Cells["C4"].Value = "F";
            worksheet.Cells["D4"].Value = 5000;

            package.Save(); //Save the workbook.
        }
        var result = PhysicalFile(Path.Combine(sWebRootFolder, sFileName), "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");

        Response.Headers["Content-Disposition"] = new ContentDispositionHeaderValue("attachment")
        {
            FileName = file.Name
        }.ToString();

        return result;
    }

If someone have better solution please post it.