load data to wpf tree view using observable collection

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WCF

WPF

My Wcf service has two data contracts called Apps and SubApps.Also I have two methods in server
side called internal List<string> GetAppIds() and internal List<string> GetSubAppIds(string AppId).
I want to load those AppIds and SubAppId into the treeview control in wpf client.when i add delete apps and subaps modifications should apply to the treeview.give me a solution to this one?

treeview structure should like below

App1
|_SubApp 1
|_SubApp 2

App2
|_SubApp 1
|_SubApp 2