Prevent Expand\collapse event of treeview and load our functionality, if shift button is pressed.

Add Event "PreviewMouseDown" for the treeview,


pTreeView->PreviewMouseDown += gcnew System::Windows::Input::MouseButtonEventHandler(this, &OnPreviewMouseDown);

void OnPreviewMouseDown( System::Object^ sender, System::Windows::Input::MouseButtonEventArgs^ e)
{

if(System::Windows::Input::Keyboard::IsKeyDown(System::Windows::Input::Key::LeftShift) ||System::Windows::Input::Keyboard::IsKeyDown(System::Windows::Input::Key::RightShift))
{
System::Windows::Controls::TreeView^ pTreeView   = nullptr;
System::Windows::DependencyObject^ pDependencyObject = (System::Windows::DependencyObject^)e->OriginalSource;

pTreeView = (System::Windows::Controls::TreeView^)sender;
FindAncestor(pDependencyObject,System::Windows::Controls::TreeViewItem::typeid);
if(pDependencyObject)
{
System::Windows::Controls::TreeViewItem^ pTreeViewItem = (System::Windows::Controls::TreeViewItem^)pDependencyObject;
int iType = m_pCtrlAdmin->GetTreeitemType( (int)pTreeViewItem->Tag );
if( pTreeViewItem->Items->Count > 0 )
{
SetTreeviewAllItemState(iType);
e->Handled = true;
}

}

}
}



void FindAncestor(System::Windows::DependencyObject^% pDependencyObject,System::Type^ pType)
{
if(pDependencyObject->GetType() == pType)
return;
else
{
pDependencyObject = System::Windows::Media::VisualTreeHelper::GetParent(pDependencyObject);
if(pDependencyObject)
FindAncestor(pDependencyObject,pType);
else
return;
}
}


void SetTreeviewAllItemState(int iType)
{
    //Write your functionality

}