title: Focus not getting set on a combobox
body: <p>I've a C#/WPF application.On my view,I need to set focus on a combobox on click of Clear button.
  My code is as per below and I dont see focus getting set on the combobox.Could you advise what am I missing here please?</p>
  
  <p>Thanks.</p>
  
  <p>MyView:</p>
  
  <pre><code>&lt;ComboBox x:Name="cboManager" Grid.Column="2" IsEnabled="{Binding EnableManagerView}" HorizontalAlignment="Left" Margin="1,1,0,0" Grid.Row="3" VerticalAlignment="Top" Width="195" Height="22" SelectedItem="{Binding MyViewModel.SelectedManager}" ItemsSource="{Binding MyViewModel.Managers}" Style="{DynamicResource ManagerStyle}" Text="{Binding MyViewModel.Manager}" DisplayMemberPath="Description" SelectedValuePath="Code" TabIndex="1"/&gt;
  </code></pre>
  
  <p>MainWindowResources.cs:</p>
  
  <pre><code>&lt;DataTrigger Binding="{Binding Path=FocusOnDealManager}" Value="true"&gt;
              &lt;Setter Property="FocusManager.FocusedElement" Value="{Binding ElementName=cboManager}"/&gt;
          &lt;/DataTrigger&gt;
  </code></pre>
  
  <p>MyViewModel:</p>
  
  <pre><code>private void Clear()
  {
  
   this.FocusOnDealManager = true;
  }
  public bool FocusOnDealManager
          {
               get; set; 
          }
  </code></pre>
  
  <p>Note: MyViewModel class inherits ViewModelBase which implements INotifyPropertyChanged interface.
  Other functionalities like setting background color on a textbox,etc. using style are working.Its just that the focus on combobox is not working.</p>
  
  <p>Thanks.</p>