QueryDeleteItem() (IVsHierarchyDeleteHandler interface) is not executing for Hierarchy Node class

Hi All,

I am working on Hierarchy Node class (VS IDE class). In my code, Hierarchy Node class is parent class for few children like ProjectNode class, FolderNode class etc. 

I have implemented IVsHierarchyDeleteHandler interface for Hierarchy Node class which contains 2 methods DeleteItem (Deletes the node) and QueryDeleteItem(Can delete node ?).

When I press 'delete' key via keyboard on FolderNode and few children, the QueryDeleteItem() from Hierarchy Node gets executed. But if i pressed 'delete' on Project Node it doesn't execute QueryDeleteItem() from Hierarchy Node class. 

I don't know why this happening for Project Node class. Even I have implemented IVsHierarchyDeleteHandler interface for Project Node class but in vain.(only to test if it is executing or not in Project Node.)

Please suggest me.