Creating Custom Project Type with Custom Project Format

[bernavs]

Is it possible to create a project type with custom format? We have our own project file which I want to open with Visual Studio.
When I try it, I've got an exception stating "The project file could not be loaded. Data at the rool level is invalid. Line 1, position 1" because our format does not match msbuild project file format. I was planning to parse the project file myself and populate the project tree with an IProjectTreeProvider.

Any help is appreciated.