title: WPF combobox set selected item on lost focus
body: <p>I have:</p>
  
  <pre><code>&lt;Combobox ItemsSouce="{Binding SomeCollection}" SelectedItem="{Binding SomeItem}" /&gt;
  </code></pre>
  
  <p>My property <code>SomeItem</code> looks like:</p>
  
  <pre><code>public object SomeItem 
  {
      get
      {
         return _someItem;
      }
      set
      {
          LogMessage("SomeItem has changed to" + value);
          _someItem = value;
          OnPropertyChanged("SomeItem");
      }
  }
  </code></pre>
  
  <p>How can I prevent calling the set method when the user scrolls through the combobox? I want to call that set method when the combobox loses focus.</p>