Neither BuiltInDocumentProperties or CustomDocumentProperties gives access to the ContentTypeProperties.
Given that many use Office in conjunction with SharePoint, I am surprised to see the lack of support for this in Aspose.Cells (or Aspose.Word, etc).
To see what I mean, do the following:
1. In WSS 3.0, create a document library.
2. In the document library, create a new column, call it "CustomCol1"). Use "Single line of text" as the type for the column.
3. Upload an Excel 2007 or Excel 2010 document into the document library.
4. Close the document, and open the document again, from the document library.
5. Click the round "Windows button", and select Prepare->Properties.
6. The so called "Document Information Panel" (DIP) appears. Make sure "Document properties - Server" is selected in the drop-down above the DIP.
7. Note that the "Custom Col1" is shown. Add a value for "Custom Col1" and save the document.
8. Go back to the document library, and note that the value you entered is shown in the document library's "Custom Col1" column.
So, in short, I want to do this but in an automated way. I can do it using VBA code (using the ThisWorkbook.ContentTypeProperties collection). However, I don't want to use VBA, I want to use Aspose.Cells (which I am using for lots of other things already). The problem is that the ContentTypeProperties collection is not exposed in Aspose.Cells...
Any ideas? This is a really important issue for us - Aspose has been working great for us, but without support for this we would have to consider using some other technology to generate our Excel documents.