title: Combobox binding and stringFormat
body: <p>I have a WPF Combobox </p>
  
  <pre><code>&lt;ComboBox SelectedValue="{Binding ElementName=Ctrl, Path=Day, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, StringFormat='00'}"
  ItemsSource="{Binding ElementName=Ctrl, Path=AvailableDays, Mode=OneWay, StringFormat='00'}"
  IsEditable="True" Grid.Column="0" /&gt;
  </code></pre>
  
  <p>which is Databound to these Properties</p>
  
  <pre><code>public int? Day {
      get { return _day; }
      set {
          if (_day != value) {
              _day = value;
              OnPropertyChanged();
          }
      }
  }
  
  public IEnumerable&lt;int&gt; AvailableDays {
      get { return _availableDays ?? (_availableDays = Enumerable.Range(1, 31)); }
  }
  </code></pre>
  
  <p>Binding works. But my issue is the Formating of the values. I want days&lt;10 to be formated with a leading zero. But my "StringFormat='00'" is completly ignored, which is odd because the same format works with a textblock without a problem.</p>