Collapsed Visibility Within a WPF ComboBoxItem

Question

I used a Style setter to stretch out my ComboBoxItem (and button) so that it spans the entire length of the ComboBox like so:

    <ComboBox >
        <ComboBox.Resources>
            <Style TargetType="ComboBoxItem">
                <Setter Property="HorizontalContentAlignment" Value="Stretch" />
            </Style>
        </ComboBox.Resources>
        <ComboBoxItem >
            <DockPanel >
                <Button Content="My Button" />
            </DockPanel>
        </ComboBoxItem>
    </ComboBox>

This works fine. Now, I add an additional button within the same ComboBoxItem, but have it set to Visibility Collapsed.

    <ComboBox >
        <ComboBox.Resources>
            <Style TargetType="ComboBoxItem">
                <Setter Property="HorizontalContentAlignment" Value="Stretch" />
            </Style>
        </ComboBox.Resources>
        <ComboBoxItem >
            <DockPanel >
                <Button Content="My Button" />
                <Button Content="My Collapsed Button" Visibility="Collapsed" />
            </DockPanel>
        </ComboBoxItem>
    </ComboBox>

Now, the new button is invisible, but I expected my original button to still stretch the entire ComboBox, like it does with the above code. However, it does not. Why is this so? Is there a solution for this? I am using DataTriggers to edit the Visibility property.

NOTE: I also get the same thing if I just set HorizontalContentAlignment="Stretch" in the ComboBox.

UPDATE: Ok, this actually has something to do with the DockPanel. I changed it to a StackPanel, and it works as desired. However, I suppose I'm still curious as to why my first button would not stretch the entire DockPanel if the second button is collapsed?

Try playing around with each of the buttons Dockpanel.Dock properties — JosephGarrone
Is there a specific reason you are using DockPanel id you change to Grid it will work fine — sa_ddam213

sa_ddam213 sa_ddam213 · Accepted Answer · 2012-12-17T05:00:43

Just set the DockPanel.Dock property to Top

  <ComboBox Margin="0,0,0,129">
      <ComboBox.Resources>
          <Style TargetType="ComboBoxItem">
              <Setter Property="HorizontalContentAlignment" Value="Stretch" />
          </Style>
      </ComboBox.Resources>
      <ComboBoxItem >
          <DockPanel >
              <Button Content="My Button" DockPanel.Dock="Top" />
              <Button Content="My Collapsed Button" Visibility="Collapsed" />
          </DockPanel>
      </ComboBoxItem>
   </ComboBox>

Collapsed Visibility Within a WPF ComboBoxItem

1 Answers