EPPlus - saving an excel created in memory and opening it on excel gives an error

问题

The objective is to create an excel file in memory and download it in the browser by using an API built in ASP.Net Core, however saving the excel as a stream and converting it to a byte array and then opening it on excel (Office 365 version 1803) gives the error: Code Byte Array:

public IActionResult Export()
{
    byte[] bytes;
    MemoryStream stream = new MemoryStream();
    using (ExcelPackage package = new ExcelPackage(stream))
    {
        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;
        bytes = package.GetAsByteArray();
    }
    return File(bytes, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "test.xlsx");
}

UPDATE: Added Memory stream example

Code Memory Stream:

public IActionResult Export()
{
    using (ExcelPackage package = new ExcelPackage())
    {
        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;
        var stream = new MemoryStream(package.GetAsByteArray());

        return File(stream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "test.xlsx");
    }
}

UPDATE 2: Created a new project with .net core 2.1 and the code works. It seems to be a project related error, somehow the content of the requests are being manipulated.. Going to investigate what is causing the issue and also post it's resolution.

回答1:

I implemented a similar scenario using package.Stream instead of package.GetAsByteArray.
(This last one also fails for me.)

Notice the package.Save which I miss in your code.
(GetAsByteArray also fails, even with Package.Save.)

public IActionResult Export()
{
    MemoryStream content = new MemoryStream(); // Gets disposed by FileStreamResult.        
    using (ExcelPackage package = new ExcelPackage(content))
    {
        // Code to create the content goes here.

        package.Save();
    }

    content.Position = 0;

    return new FileStreamResult(content, "application/octet-stream") { 
        FileDownloadName = "test.xlsx"
        };            
}  

来源：https://stackoverflow.com/questions/51652745/epplus-saving-an-excel-created-in-memory-and-opening-it-on-excel-gives-an-erro