[asp.net-mvc] Export data to Excel file with ASP.NET MVC 4 C# is rendering into view

  using (MemoryStream mem = new MemoryStream())
  {
    SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.Create(mem, SpreadsheetDocumentType.Workbook);

    // Add a WorkbookPart to the document.
    WorkbookPart workbookpart = spreadsheetDocument.AddWorkbookPart();
    workbookpart.Workbook = new Workbook();

    // Add a WorksheetPart to the WorkbookPart.
    WorksheetPart worksheetPart = workbookpart.AddNewPart<WorksheetPart>();
    worksheetPart.Worksheet = new Worksheet(new SheetData());

    // Add Sheets to the Workbook.
    Sheets sheets = spreadsheetDocument.WorkbookPart.Workbook.AppendChild<Sheets>(new Sheets());

    SheetData sheetData = worksheetPart.Worksheet.GetFirstChild<SheetData>();

    // Add a row to the cell table.
    Row row;
    row = new Row() { RowIndex = 1 };
    sheetData.Append(row);

    // In the new row, find the column location to insert a cell in A1.  
    Cell refCell = null;
    foreach (Cell cell in row.Elements<Cell>())
    {
      if (string.Compare(cell.CellReference.Value, "A1", true) > 0)
      {
        refCell = cell;
        break;
      }
    }

    // Add the cell to the cell table at A1.
    Cell newCell = new Cell() { CellReference = "A1" };
    row.InsertBefore(newCell, refCell);

    // Set the cell value to be a numeric value of 100.
    newCell.CellValue = new CellValue("100");
    newCell.DataType = new EnumValue<CellValues>(CellValues.Number);

    // Append a new worksheet and associate it with the workbook.
    Sheet sheet = new Sheet()
    {
      Id = spreadsheetDocument.WorkbookPart.GetIdOfPart(worksheetPart),
      SheetId = 1,
      Name = "mySheet"
    };

    sheets.Append(sheet);

    workbookpart.Workbook.Save();
    spreadsheetDocument.Close();

    return File(mem.ToArray(), System.Net.Mime.MediaTypeNames.Application.Octet, "text.xlsx");
  }