Hello Le Thanh,
In order to react on user property changes, your user class have to implement the INotifyPropertyChanged
interface and you will have to raise the PropertyChanged
In order to group the users, you will have to create groups and specify the group a user should be assigned to. Later when you change the user's properties you can also change the groups they belong to. I have also added sorting just to give you basic idea.
I have attached a sample project to show you everything in action.
Hope this helps. Please let me know if you have further questions.
the Telerik team