title: Cant bind enum to combobox wpf mvvm
body: <p>A have read a lot of method about the ways of binding enum to combobox. So now in .Net 4.5 it should be pretty ease. But my code dont work.
  Dont really understand why.</p>
  
  <p>xaml:</p>
  
  <pre><code>&lt;Window x:Class="SmartTrader.Windows.SyncOfflineDataWindow"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="SyncOfflineDataWindow" Height="300" Width="300"&gt;
  &lt;Grid&gt;
      &lt;StackPanel&gt;
          &lt;ComboBox ItemsSource="{Binding StrategyTypes}" SelectedItem="{Binding StrategyType}" /&gt;
          &lt;Button Width="150" Margin="5" Padding="5" Click="Button_Click"&gt;Save&lt;/Button&gt;
      &lt;/StackPanel&gt;
  &lt;/Grid&gt;
  </code></pre>
  
  <p></p>
  
  <p>xaml.cs backend</p>
  
  <pre><code>namespace SmartTrader.Windows
  {
      /// &lt;summary&gt;
      /// Interaction logic for SyncOfflineDataWindow.xaml
      /// &lt;/summary&gt;
      public partial class SyncOfflineDataWindow : Window
      {
          public SyncOfflineDataWindow(IPosition position, ContractType type)
          {
              DataContext = new ObservablePosition(position);
              InitializeComponent();
          }
  
          private void Button_Click(object sender, RoutedEventArgs e)
          {
  
          }
      }
  }
  </code></pre>
  
  <p>View Model:</p>
  
  <pre><code>namespace SmartTrader.Entity
  {
      public class ObservablePosition : NotifyPropertyChanged, IPosition
      {
          public IEnumerable&lt;StrategyType&gt; StrategyTypes =
              Enum.GetValues(typeof (StrategyType)).Cast&lt;StrategyType&gt;();
  
          public ObservablePosition(IPosition position)
          {
             Strategy = position.Strategy;
          }
  
  
          private StrategyType _strategyType = StrategyType.None;
          public StrategyType Strategy
          {
              get { return _strategyType; }
              set
              {
                  _strategyType = value;
                  OnPropertyChanged();
              }
          }
      }
  }
  </code></pre>
  
  <p>StrategyType is enum.
  All i have got it is empty dropdown list<img src="https://i.stack.imgur.com/MgMz3.png" alt="empty combox"></p>