public override void SetNeedsBuilding (IBuildTarget item, bool val, ConfigurationSelector configuration) { if (item is SolutionItem) { SolutionItem entry = (SolutionItem) item; entry.OnSetNeedsBuilding (val, configuration); } else if (item is WorkspaceItem) { ((WorkspaceItem)item).OnSetNeedsBuilding (val, configuration); } else throw new InvalidOperationException ("Unknown item type: " + item); }