This is very common scenario for Silverlight
ItemsControls (not only Telerik controls) that provide SelectedItem and SelectedItems properties as they cannot be assigned to in XAML - they are read-only and you cannot bind two-way to them.
There are two ways you can choose from to solve this without breaking the MVVM pattern:
1. Add IsSelected boolean property to your Business Objects class and use it to know which Items are selected.
2. Implement a custom behaviour, commonly referred to as Blend behaviour. You define a Blend behaviour by creating a non-static class that derives from the System.Windows.Interactivity.Behavior<T> class. Note that this abstract base class doesn’t ship with the .NET Framework but it is part of the Microsoft Expression Blend SDK that can be downloaded from Microsoft’s official website here. You will need to reference the System.Windows.Interactivity.dll from your application or class library. You can then easily add the above behaviour to the TreeView control as shown in the markup below:
Both approaches are mentioned (together with code snippets) in this
stackoverflow post. Use whatever is more suitable for your scenario.
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