c# - How to set children Width for DockPanel to 100% inside ComboxItem? -

<comboboxitem horizontalcontentalignment="stretch" width="auto">      <dockpanel background="red" horizontalalignment="stretch" lastchildfill="true" width="auto">         <label dockpanel.dock="left" name="lbname" ></label>         <image dockpanel.dock="right" horizontalalignment="right" name="image" source="/test;component/images/cross.jpg" width="16" height="16" stretch="uniformtofill" />         <image dockpanel.dock="right" horizontalalignment="right" name="image2" source="/test;component/images/cross.jpg" width="16" height="16" stretch="uniformtofill" />     </dockpanel> </comboboxitem> 

like can see on image below dockpanel(marked red) doesn't take 100% width of comboboxitem.

how stretch dockpanel size of comboboxitem in xaml?

it turns out, content of comboboxitem filled entire space, when event selectionchanged triggered.

example:

xaml

<combobox width="300"           height="30"           selectionchanged="combobox_selectionchanged">      <comboboxitem>test</comboboxitem>      <comboboxitem name="comboboxitem"                   horizontalcontentalignment="stretch"                                             width="auto">          <dockpanel background="red"                     horizontalalignment="stretch"                     width="auto">                                 ...         </dockpanel>     </comboboxitem> </combobox> 

code-behind

private void combobox_selectionchanged(object sender, selectionchangedeventargs e) {     messagebox.show(comboboxitem.actualwidth.tostring()); } 

when start application actualwidth of comboboxitem zero, when selectionchanged event triggered value 298.

workaround

for workaround add comboboxitem in begin, example: select item , set combobox selectedindex="0" this:

<combobox width="300"           height="30"           selectedindex="0">      <comboboxitem>select item</comboboxitem>     ...