ListBox与ItemTemplate（和ScrollBar！）

Question

I have a databound and itemtemplated ListBox:

<ListBox x:Name="lbLista" 
         ScrollViewer.VerticalScrollBarVisibility="Visible">
    <ListBox.ItemTemplate>
      <DataTemplate>
        <StackPanel Orientation="Horizontal">
          <CheckBox IsChecked="{Binding Deleteable, Mode=TwoWay}" />
          <Label Content="{Binding Name}" />
        </StackPanel>
      </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

The ites show fine and they come from an ObservableCollection.

The problem is the scrollbar which appears but is not usable - it does not have a handle to grab. I've tried setting some ScrollView attached properties on ListBox, but they do not affect the situation.

Answer 1

I pasted your code into test project, added about 20 items and I get usable scroll bars, no problem, and they work as expected. When I only add a couple items (such that scrolling is unnecessary) I get no usable scrollbar. Could this be the case? that you are not adding enough items?

If you remove the ScrollViewer.VerticalScrollBarVisibility="Visible" then the scroll bars only appear when you have need of them.

Answer 2

ListBox will try to expand in height that is available.. When you set the Height property of ListBox you get a scrollviewer that actually works...

If you wish your ListBox to accodate the height available, you might want to try to regulate the Height from your parent controls.. In a Grid for example, setting the Height to Auto in your RowDefinition might do the trick...

HTH

Answer 3

I have never had any luck with any scrollable content placed inside a stackpanel (anything derived from ScrollableContainer. The stackpanel has an odd layout mechanism that confuses child controls when the measure operation is completed and I found the vertical size ends up infinite, therefore not constrained - so it goes beyond the boundaries of the container and ends up clipped. The scrollbar doesn't show because the control thinks it has all the space in the world when it doesn't.

You should always place scrollable content inside a container that can resolve to a known height during its layout operation at runtime so that the scrollbars size appropriately. The parent container up in the visual tree must be able to resolve to an actual height, and this happens in the grid if you set the height of the RowDefinition o to auto or fixed.

This also happens in Silverlight.

-em-

Answer 4

Thnaks for answer. I tried it myself too to an Empty Project and - lo behold allmighty creator of heaven and seven seas - it worked. I originally had ListBox inside which was inside of root . For some reason ListBox doesn't like being inside of StackPanel, at all! =)

-pom-