Hi Balaram Barange,
I have two suggestions:
1. If you want to hide only some of the children - then you will be able to set their visibility. You can also bind the visibility of the item container using ContainerBindings (similar to WPF's Style Bindings, but added as an attached collection to the DataTemplate).
Do you need more help with the container bindings?
2. If you want to hide all the children, collapsing them will not work since the expand button will still be visible. If you want to hide them, it is best to change the collection property (i.e. not the collection itself) of their parent. Just make sure that the items source that has generated the items is an observable property. (The property that you bind to in the hierarchical data template). Then, when you want to hide the items , raise the OnChanged event and make sure the property returns an empty Enumerable (Empty collection) from then on. Since you may be using the property yourself, better create another property that will change when you need it and keep the actual collection property always returning what you expect it to.
Hopefully this will work for you,
All the best,
the Telerik team