Error dialog displayed when opening an excel file generated with EPPlus

Question

I am creating an Excel file using the EPPlus library. When I create file and open up the file, the following pop up message shows:

We found a problem with some content in 'ExcelDemo.xlsx'. Do you want us to try to recover as much as we can? If you trust the source of this workbook, Click Yes

I am using following code

using (ExcelPackage pck = new ExcelPackage())
{
    //Create the worksheet
    ExcelWorksheet ws = pck.Workbook.Worksheets.Add("Demo");

    //Load the datatable into the sheet, starting from cell A1. Print the column names on row 1
    ws.Cells[1, 2].Value = "Excel Download";

    Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
    Response.AddHeader("content-disposition", "attachment;  filename=ExcelDemo.xlsx");
    Response.BinaryWrite(pck.GetAsByteArray());
}

Is there problem in my code or is this an Excel issue?

Answer 1

At the start, you need to add in a:

Response.Clear();

Then at the end add a

Response.End();

Answer 2

In my case the problem was in calling

package.Save();

and using

Response.BinaryWrite(package.GetAsByteArray());

at the same time.

When you call package.GetAsByteArray() it perfoms following operations internally:

this.Workbook.Save();
this._package.Close();
this._package.Save(this._stream);

So, calling package.Save two times leads to this error when opening in Excel.