Convert .XLSX or .XLSM to XML

Question

I have the code below which I using to programmatically save a Office 2010 Excel Spreadsheet to XML. This code generates a perfect XML document with a schema that matches the Excel Save As option. My question is there a way to achieve this without using the interop assemblies. I have looked through the Open XML documentation and I can't find a "Save As" option that will allow me to save the document as xml. Is this possible? Any help in c# or vb.net would be appreciated.

 Private Function ConvertExcelToXml(path As String, file As String) As Boolean
    Dim returnValue as Boolean
    returnValue = True
    Try
        Dim importfile As String = (path & file) + ".xlsm"
        Dim exportfile As String = (path & file) + ".xml"
        Dim app As New Application()
        app.Workbooks.Open(importfile, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing,
                           Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing,
                           Type.Missing, Type.Missing, Type.Missing)
        Dim data As String = String.Empty

        app.ActiveWorkbook.XmlMaps(1).ExportXml(data)  'export the excel sheet xml to the string variable
        System.IO.File.Delete(exportfile)   'delete the file if it already exists
        System.IO.File.WriteAllText(exportfile, data) 'write the new file
        app.Workbooks.Close()
    Catch ex As Exception
        returnValue = false
    End Try
    return returnValue
End Function

Thanks, Chaos

Answer 1

In short, interop is the best and possibly only out of the box solution for what you want to achieve.

Some possible leads that could work are:

1. Spire.XLS which can be found here for free. It looks like it might support exporting to XML given a schema but I wouldn't bet on it given a superficial browsing.
2. ClosedXML, a wrapper around OpenXML which provides a more application like interface to the underlying data. From browsing the source code and documentation I don't fancy your chances of exporting xml maps.

You could roll you own of course using OpenXML to get the content of an XML mapping and so on. An answer to how XML maps work in OpenXML points to the CustomXmlMappingsPart if you want to take that path.

My recommendation however is to accept that interop is excel and the pros come with the cons.