title: Binding the selected item in an inner ListBox in WPF
body: <p>I am having trouble binding selected item of a ListBox in my application
  (IDE : Visual Studio 2010, Language : C#, Technology : WPF and MVVM). </p>
  
  <p>Requirement: There is a list of interfaces and another list of devices 
  connected to each interface. The pattern of displaying these 2 lists is as
  follows:</p>
  
  <p>Interface 1</p>
  
  <pre><code>Device 1
  
  Device 2
  
  Device 3
  </code></pre>
  
  <p>Interface 2</p>
  
  <pre><code>Device 1
  
  Device 2
  </code></pre>
  
  <p>Interface 3</p>
  
  <pre><code>Device 1
  
  Device 2
  
  Device 3
  
  Device 4
  </code></pre>
  
  <p>and so on.</p>
  
  <p>If any interface is selected then by default the first device must be 
  selected and if any device is selected then the corresponding interface
  must be selected. I am able to do the first part but not the second part.
  How can I make the selected Item to be unique across all the inner list 
  of devices?</p>
  
  <p>I want to display the above list as a list of expanders where each exapander will have the following format:
  Expander header : Interface name
  Expander Body : List of connected devices</p>
  
  <p>I hope I am clear.</p>
  
  <p>Please do tell me if there is any wpf control for this or should I develop
  a new ListBox for this?</p>
  
  <p>Regards
  Kruthika</p>