title: Editable WPF ComboBox does not fire PropertyChanged
body: <p>I have a not editable ComboBox to display all tables of and SQL Database.</p>
  
  <pre><code> &lt;ComboBox Grid.Column="1" 
                        Grid.Row="2" 
                        Height="23"  
                        Margin="3,3,3,3" Name="cbLogTable" VerticalAlignment="Top"
                        ItemsSource="{Binding}"
                        TextSearch.TextPath="TABLE_NAME"
                        SelectedValue="{Binding Path=LogTable, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay, ValidatesOnDataErrors=True}"
                        &gt;
                  &lt;ComboBox.ItemTemplate&gt;
                      &lt;DataTemplate&gt;
                          &lt;StackPanel&gt;
                              &lt;TextBlock Text="{Binding Path=TABLE_NAME}"/&gt;
                          &lt;/StackPanel&gt;
  
                      &lt;/DataTemplate&gt;
                  &lt;/ComboBox.ItemTemplate&gt;
              &lt;/ComboBox&gt;
  </code></pre>
  
  <p>The property of the containing UserControl looks like this and also implements the INotifyPropertyChanged:</p>
  
  <pre><code>    public string LogTable
      {
          get
          {
              return _logTable;
          }
          set
          {
              if (_logTable == value) return;
              _logTable = value;
              OnPropertyChanged("LogTable");
          }
       }
  </code></pre>
  
  <p>I use the following data binding to fill the ComboBox:</p>
  
  <pre><code>    private void UpdateLogTable()
      {
          var connection = new SqlConnection(_connectionString);
          connection.Open();
          DataTable t = connection.GetSchema("Tables");
          cbLogTable.DataContext = t;
          connection.Close();
      }
  </code></pre>
  
  <p>But I don't receive a PropertyChanged notification on changing the selected value of the ComboBox. Where is my fault?</p>