What's a .duo file?

In a .NET/C# project, one of my *.exe files has a corresponding *.duo file. (I didn't set up the build system.) What is it?

Somebody suggested it was something like a use开发者_开发百科r preferences file for the debugger, possibly?

I think it might mean database user options, because it seems to have some form of relation with Microsoft Access.

Did you mean .suo? That stands for Visual Studio Solution User Options.

Seems to be database related

I can't seem to find any info on the file extension : http://filext.com/alphalist.php?extstart=^D

Additionally - it does not appear to be a valid Visual Studio file extension - are you using any 3rd party tools that might generate this? What are you using for source control?