Creation of viewmodel for treeview in WPF with grouping of objects
<p>I am creating an application for chatting in WPF(C#.net).
I have created a class User with following attributes:
1.Company_name 
2.Branch 
3.Designation 
4.User_name 
I am getting the list of objects of class user.
I want to display the users in treeview as:</p>

<p>Company name1
      -Branch1
            -:Designation1
                  *User name1
                  *User name2
      -Branch2
            -:Designation1
                  *User name3
            -:Designation2
                  *User name4</p>

<p>when user list is refreshed, the tree structure will reloaded. 
I want to create this tree structure considering users with same parent. 
I am getting the user list at run time when a new user logs in.
 How to create such tree?
I want to know, how to create such treeview using "ViewModel and display it in WPF window"??</p>
