title: WPF binding textbox to dictionary entry
body: <p>i try to bind a wpf textbox to a dictionary placed in a viewmodel. The viewmodel is used as datacontext for the view.
  I found a lot of examples and it sounds simple, but it will not work for me.</p>
  
  <p>View:</p>
  
  <blockquote>
    <p>TextBox x:Name="txbTest" Grid.Row="10" Grid.Column="2" Text="{Binding MyDict[First]}"</p>
  </blockquote>
  
  <p>ViewModel:</p>
  
  <pre><code>public Dictionary&lt;string, string&gt; MyDict = new Dictionary&lt;string, string&gt;
          {
              {"First", "Test1"},
              {"Second", "Test2"}
          };
  </code></pre>
  
  <p>I try all variants i found</p>
  
  <pre><code>Text="{Binding MyDict[First]}"
  Text="{Binding Path=MyDict[First]}"
  Text="{Binding MyDict[First].Text}"
  Text="{Binding MyDict[First].Value}"
  </code></pre>
  
  <p>But nothing works, textbox is empty. Any idea?</p>