使用OpenXML从MVC Controller中读取工作簿

Question

I am generating an Excel Document from MVC using Open XML.

The code is as below:

public ActionResult ExcelReport()
{
  var custId = 1234; //ToDo get from session when it is set

  using (MemoryStream mem = new MemoryStream())
  {
    ExcelReportGenerator excel = new ExcelReportGenerator();

    excel.CreateExcelDoc(mem);

    var reportName = string.Format("MyReport_{0}.xlsx", custId);

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

}

My CreateExcelDoc method is as below:

public void CreateExcelDoc(MemoryStream mem)
{
  SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.Create(mem, SpreadsheetDocumentType.Workbook);

  //SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.Open(mem, false);

  //Code removed for brevity 

  worksheetPart.Worksheet.Save();
  spreadsheetDocument.Close();

}

With the create method the excel sheet is downloading as expected. However, I wanted to make the workbook read-only so was trying the .Open method passing the mem stream and the isEditable set to false but I am getting a YSOD when I hit the controller with an Error Exception Details: System.IO.FileFormatException: Archive file cannot be size 0.

Answer 1

A simpler way of making your excel read only is to Protect the worksheet (see Step 2 at link) .

The OpenXML code to do this is one line per sheet:

workSheet.Append(new SheetProtection() { Sheet = true, Objects = true, Scenarios = true });

I have pushed a new version of the reference implementation MVC that uses this technique. The SheetProtection seems to be supported in Excel 2007, where the marking as Final is only supported since Excel 2013.

Answer 2

The call SpreadsheetDocument.Open does not result in a read only file. It merely opens the memory stream in read only mode. ( isEditable is false) This locks the stream from being changed by the rest your code. This explains why you were likely generating an excel fine before you added that call, and why you are getting the empty archive exception after you added that call. Do not use SpreadsheetDocument.Open for that purpose.

I do not recommend you try to send your Excel as a read only file. The user can download it on any operating system and rename it and change the file permissions as they want to.

What I recommend is add openXML code that mark your Excel as final . Microsoft added this capability to Office documents as it more formally discourages users from making future changes to the file instead of simple file permissions. Any changes to one of these files, requires a new filename.

The recommended OpenXml code will generate a Custom Property so when the user downloads the file, it will be marked as Final to discourage user edits.

Here is the method that will add the custom property:

private void GenerateCustomFilePropertiesPart1Content(CustomFilePropertiesPart customFilePropertiesPart1)
    {
        Op.Properties properties2 = new Op.Properties();
        properties2.AddNamespaceDeclaration("vt", "http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes");

        Op.CustomDocumentProperty customDocumentProperty1 = new Op.CustomDocumentProperty() { FormatId = "{D5CDD505-2E9C-101B-9397-08002B2CF9AE}", PropertyId = 2, Name = "_MarkAsFinal" };
        Vt.VTBool vTBool1 = new Vt.VTBool();
        vTBool1.Text = "true";

        customDocumentProperty1.Append(vTBool1);

        properties2.Append(customDocumentProperty1);

        customFilePropertiesPart1.Properties = properties2;
    }

I have written a simple MVC app that generates an empty Excel file marked as final for you as a reference implementation. The code is hosted on GitHub . When you run it, click on the rightmost menu link "Download Excel". This will download an Excel with one Workbook named Walter's Workbook and no data. The excel will be marked as final. The code for Custom Property was generated with the OpenXML Productivity Tool. Good luck with your project.