void CollectBuildableEntries(HashSet <SolutionItem> collected, ConfigurationSelector configuration, SolutionConfiguration slnConf, bool includeDependencies)
 {
     foreach (SolutionFolderItem item in Items)
     {
         if (item is SolutionFolder sf)
         {
             sf.CollectBuildableEntries(collected, configuration, slnConf, includeDependencies);
         }
         else if (item is SolutionItem si && slnConf.BuildEnabledForItem(si) && si.SupportsBuild() && collected.Add(si))
         {
             if (includeDependencies)
             {
                 Solution.CollectBuildableDependencies(collected, si, configuration, slnConf);
             }
         }
     }
 }