we use StyleCop and it checks whether each source file has our copyright header. This is fine till I add an opensource file with its own header, and the two now are conflicting. How can I turn off Stylecop check for particular files and messagetypes in project?
If you want StyleCop to completely ignore these files, you can add ExcludeFromStyleCop elements within your .csproj file as described at http://stylecop.codeplex.com/wikipage?title=Using%20StyleCop%20on%20Legacy%20Projects.
If you want to deactivate only certain rules for these files, this can be done by adding a SourceFileList section to your StyleCop.settings files as described at http://stylecop.codeplex.com/wikipage?title=Using%20File%20Lists.