The most straightforward way to download a file in mvc - asp.net

Question

I am currently saving an excel file like so on my c drive.
public ActionResult Export()
{
try
{
Excel.Application application = new Excel.Application();
Excel.Workbook workbook = application.Workbooks.Add(System.Reflection.Missing.Value);
Excel.Worksheet worksheet = workbook.ActiveSheet;
var people = db.People.ToList();
worksheet.Cells[1, 1] = "Last Name";
worksheet.Cells[1, 2] = "First Name";
int row = 2;
foreach (var person in people)
{
worksheet.Cells[row, 1] = person.PersonFName;
worksheet.Cells[row, 2] = person.PersonLName;
row++;
}
workbook.SaveAs("c:\\test\\worksheet.xls");
workbook.Close();
Marshal.ReleaseComObject(workbook);
application.Quit();
Marshal.FinalReleaseComObject(application);
ViewBag.Result = "Done";
}
catch(Exception ex)
{
ViewBag.Result = ex.Message;
}
return File("c:\\test\\workseet.xls", "application/vnd.ms-excel", "workseet.xls");
// return View("Success");
}
I can go to c:\\test\workseet.xls and it exists there I can do what ever with it...
I am wanting to transform my method from return a view to return a file download...
I figured that it was as simple as this:
return File("c:\\test\\workseet.xls", "application/vnd.ms-excel", "workseet.xls");
However when I do this method and click the link to download, it gives me this error.
The process cannot access the file 'c:\test\workseet.xls' because it is being used by another process.

Answer 1

This duplicate question is just one of those that show how to use EPPlus to generate Excel files on the server side in a scaleable manner. It's actually a lot easier than using Excel interop and a lot faster. You don't even have to save the file to the disk.
public ActionResult ExportData()
{
//Somehow, load data to a DataTable
using (ExcelPackage package = new ExcelPackage())
{
var ws = package.Workbook.Worksheets.Add("My Sheet");
//true generates headers
ws.Cells["A1"].LoadFromDataTable(dataTable, true);
//Save the workbook to a stream
var stream = new MemoryStream();
package.SaveAs(stream);
string fileName = "myfilename.xlsx";
string contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
stream.Position = 0;
return File(stream, contentType, fileName);
}
}
You can use LoadFromDataTable to fill a sheet from a data table or LoadFromCollection to load data from a collection, eg List<Sale>.
Both methods return an ExcelRange object (a range of cells) that you can use to format individual cells, rows, and columns. You can also create tables from a range and apply themes.
The duplicate goes even farther and shows how you can avoid even the MemoryStream