title: When typing in editable ComboBox not showing DropDown list
body: <p>I'm working with <code>ComboBox</code> in WPF. <code>ComboBox</code> IsEditable property setted to True<code>IsEditable="True"</code>. <code>ComboBox</code> has several items. When I'm typing it is showing item in <code>ComboBox</code> text, but not showing DropDown list. 
  <strong>XAML code:</strong></p>
  
  <pre><code> &lt;ComboBox Name="uiComboBox" IsEditable="True"&gt;
          &lt;ComboBoxItem&gt;One1&lt;/ComboBoxItem&gt;
          &lt;ComboBoxItem&gt;One2&lt;/ComboBoxItem&gt;
          &lt;ComboBoxItem&gt;One3&lt;/ComboBoxItem&gt;
          &lt;ComboBoxItem&gt;One4&lt;/ComboBoxItem&gt;
          &lt;ComboBoxItem&gt;Two&lt;/ComboBoxItem&gt;
          &lt;ComboBoxItem&gt;Three&lt;/ComboBoxItem&gt;
      &lt;/ComboBox&gt;
  </code></pre>
  
  <p>When I typing  "o" showing first item that starts with "o", in this case it is "One1"
  <img src="https://i.stack.imgur.com/g9sWL.png" alt="enter image description here"></p>
  
  <p>When I  type "o" it should show me DropDown list with items that starts with "o" in this case 4 items, you can see in picture in below.<img src="https://i.stack.imgur.com/kciwF.png" alt="enter image description here"></p>
  
  <p>After researching I found:</p>
  
  <pre><code> private void ComboBox_KeyUp(object sender, KeyEventArgs e)
      {
          uiComboBox.IsDropDownOpen = true;
      }
  </code></pre>
  
  <p>It is showing all not items that starts with letter i typed.
  Any ideas to do that or maybe another control to use for this case?</p>