R – Interop with Office 2003 and 2007

interopms-office

I would like to have my application function with both version of Office (as well as Outlook within those). I understand I can't install them full in parallel (Outlook being the fight really).

In specific, our application opens up Outlook, fills some information and loads up the contacts (so they can select who to send it to), and some other basics. If it matters, the OS varies from Windows SP, Server 2003, Server 2008, and Vista.

We're considering going to Office 2007 (going to have to sooner or later whether we like it or not, so I'm preparing sooner rather than later) and if I install Office 2007 I find I can't use the older interop dll (app won't compile). I'm left to assume that if I use the 2007 interop that 2003 won't work — which is what we're on now.

Other apps do this but my Google foo fails me and my StackOverflow foo is about the same.

Any thoughts on how to get Visual Studio to allow me to code for both?

edit:
I actually forgot about this question however I have the answer.

The answer was the cause from something else. The Interop worked just fine however another bit of code referenced another version specific reference (of Excel, to be specific) instead of Interop. Having never worked with Interop before, I just assumed it didn't matter and they were one and the same. Turns out I was wrong. Once we removed all the referenced and re-added back normal Microsoft.Office.Interop references, it all Just Worked (TM).

Best Answer

Err, so the question can close I'll add the answer here:

The answer was the cause from something else. The Interop worked just fine however another bit of code referenced another version specific reference (of Excel, to be specific) instead of Interop. Having never worked with Interop before, I just assumed it didn't matter and they were one and the same. Turns out I was wrong. Once we removed all the referenced and re-added back normal Microsoft.Office.Interop references, it all Just Worked (TM).

Related Solutions

C# – How to properly clean up Excel interop objects

Excel does not quit because your application is still holding references to COM objects.

I guess you're invoking at least one member of a COM object without assigning it to a variable.

For me it was the excelApp.Worksheets object which I directly used without assigning it to a variable:

Worksheet sheet = excelApp.Worksheets.Open(...);
...
Marshal.ReleaseComObject(sheet);

I didn't know that internally C# created a wrapper for the Worksheets COM object which didn't get released by my code (because I wasn't aware of it) and was the cause why Excel was not unloaded.

I found the solution to my problem on this page, which also has a nice rule for the usage of COM objects in C#:

Never use two dots with COM objects.

So with this knowledge the right way of doing the above is:

Worksheets sheets = excelApp.Worksheets; // <-- The important part
Worksheet sheet = sheets.Open(...);
...
Marshal.ReleaseComObject(sheets);
Marshal.ReleaseComObject(sheet);

POST MORTEM UPDATE:

I want every reader to read this answer by Hans Passant very carefully as it explains the trap I and lots of other developers stumbled into. When I wrote this answer years ago I didn't know about the effect the debugger has to the garbage collector and drew the wrong conclusions. I keep my answer unaltered for the sake of history but please read this link and don't go the way of "the two dots": Understanding garbage collection in .NET and Clean up Excel Interop Objects with IDisposable

C# – Vista, Office Interop not working

You should really avoiding running the Office clients as server side apps. Consider using xml as file format (xlsx for Office 2007, or using the Excel workbook xsd for (somewhat) older versions.) Then you would be freed from using the Excel API on the server.

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