title: ComboBox selection change breaks DataTrigger
body: <p>I am trying to set the selected value of a combobox from a style trigger.It works as long as we dont manually change any value in the combobox.But it stops working altogether after manually changing the selection.How  can i solve this.A sample code is attached.Please do help</p>
  
  <pre><code>&lt;Window x:Class="InputGesture.Window2"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:local="clr-namespace:InputGesture"
      Title="Window2" Height="300" Width="300" Name="Sample"&gt;
      &lt;Window.Resources&gt;
          &lt;Style TargetType="{x:Type ComboBox}"&gt;
              &lt;Setter Property="ComboBox.SelectedValue" Value="1"/&gt;
              &lt;Style.Triggers&gt;
                  &lt;DataTrigger Binding="{Binding ElementName=chk,Path=IsChecked}" Value="True"&gt;
                      &lt;Setter Property="ComboBox.IsEnabled" Value="False"/&gt;
                      &lt;Setter Property="ComboBox.SelectedValue" Value="2"/&gt;
                  &lt;/DataTrigger&gt;
              &lt;/Style.Triggers&gt;
              &lt;/Style&gt;
      &lt;/Window.Resources&gt;
      &lt;StackPanel&gt;
          &lt;CheckBox Name="chk" Height="23"/&gt;
          &lt;ComboBox Name="cmb" Height="23" DisplayMemberPath="Name"             
                    SelectedValuePath="Id" ItemsSource="{Binding ElementName=Sample,Path=DT}"&gt;
          &lt;/ComboBox&gt;
  
          &lt;Button Height="23" Click="Button_Click"/&gt;
      &lt;/StackPanel&gt;
  &lt;/Window&gt;
  </code></pre>