title: MaterialDesignXamlToolkit wpf dialoghost buttons are disabled when opened
body: <p>I am using the MaterialDesignThemes nuget package along with the Mahapps.Metro package</p>
  
  <p>I have this DialogHost</p>
  
  <pre><code>&lt;material:DialogHost Name="PopupAddCustom" HorizontalAlignment="Center" VerticalAlignment="Center" IsOpen="False" &gt;
      &lt;material:DialogHost.DialogContent&gt;
          &lt;StackPanel Margin="16" Orientation="Vertical"&gt;
              &lt;Label Content="Add custom date" FontSize="16" /&gt;
              &lt;DatePicker /&gt;
              &lt;StackPanel Orientation="Horizontal"&gt;
                  &lt;Button Content="ACCEPT" Style="{DynamicResource MaterialDesignFlatButton}" IsDefault="True" Margin="0,8,8,0" Command="material:DialogHost.CloseDialogCommand" CommandParameter="True" /&gt;
                  &lt;Button Content="CANCEL" Style="{DynamicResource MaterialDesignFlatButton}" IsCancel="True" Margin="0,8,8,0" Command="material:DialogHost.CloseDialogCommand" CommandParameter="False" /&gt;
              &lt;/StackPanel&gt;
          &lt;/StackPanel&gt;
      &lt;/material:DialogHost.DialogContent&gt;
  &lt;/material:DialogHost&gt;
  </code></pre>
  
  <p>That is being openend by this button</p>
  
  <pre><code>&lt;Button MinWidth="120" Margin="10" Style="{StaticResource MaterialDesignRaisedAccentButton}" ToolTip="Add in a new custom date." Command="{x:Static material:DialogHost.OpenDialogCommand}" CommandTarget="{Binding ElementName=PopupAddCustom}"  &gt;
      &lt;StackPanel Orientation="Horizontal"&gt;
          &lt;Rectangle Width="20" Height="20" Fill="{Binding RelativeSource={RelativeSource AncestorType=Button}, Path=Foreground}"&gt;
              &lt;Rectangle.OpacityMask&gt;
                  &lt;VisualBrush Stretch="Fill" Visual="{StaticResource fa_plus}" /&gt;
              &lt;/Rectangle.OpacityMask&gt;
          &lt;/Rectangle&gt;
          &lt;TextBlock Margin="10,0,0,0" VerticalAlignment="Center" Text="Custom" /&gt;
      &lt;/StackPanel&gt;
  &lt;/Button&gt;
  </code></pre>
  
  <p>However when this dialog gets opened the ACCEPT and CANCEL buttons are disabled. So to check if anything was wrong I manually opened this dialog from the my MainWindow constructor like this</p>
  
  <pre><code>this.Loaded += delegate(object sender, RoutedEventArgs args)
  {
      this.PopupAddCustom.IsOpen = true;
  };
  </code></pre>
  
  <p>When I open the dialog like this the button are in working order, am I missing something obvious here?</p>