#pragma warning disable VSTHRD010 // Accessing ... should only be done on the main thread.
static IEnumerable <ProjectItem> GetDescendants(ProjectItem projectItem)
{
// VS will run the custom tool on the project item only if the document is open => Run the custom tool on any of the descendants, too.
// VS will not run the custom tool if just the file is saved in background, and no document is open => Run the custom tool on all descendants and self.
return(projectItem.GetIsOpen() ? projectItem.Descendants() : projectItem.DescendantsAndSelf());
}