如何使用 ListBox 作为基础 class？

Question

I use ListBox to show some grid. I want to create some class that will be based on (derived from) the ListBox and to change the ItemTemplate of this derived class.

How can i do it?

I try to define a class that derives from UserControl class - and change the derived class to be ListBox beside the UserControl class - but this doesn't work.

Is there any other way?

I need to have the ability to change the ListBoxItem template in the ListBox like I do in the ListBox that I add to simple silverlight page.

Thanks for any help.

Answer 1

what you can do is to create a templated control (you can easily create one via visual studios Add - New Item menu) whcich you derive from ListBox:

public class MyListBox : ListBox
{
    public MyListBox()
    {
        this.DefaultStyleKey = typeof(MyListBox);
    }
}

When you create a templated control it will also create the folder Themes and in there a generic.xaml where your styles are defined. After that take the ListBox - Style from here and copy and paste it in your generic.xaml at the right position (you need the ValidationTooltipTemplate, too):

<Style TargetType="local:MyListBox">
        <Setter Property="Padding" Value="1"/>
        <Setter Property="Background" Value="#FFFFFFFF" />
        <Setter Property="Foreground" Value="#FF000000"/>
        <Setter Property="HorizontalContentAlignment" Value="Left" />
        <Setter Property="VerticalContentAlignment" Value="Top" />
        <Setter Property="IsTabStop" Value="False" />
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="TabNavigation" Value="Once" />
        <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
        <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
        <Setter Property="BorderBrush"> ...

Ok, after that define you ItemTemplate in the same xaml:

<DataTemplate x:Key="MyItemTemplate">

and add it to the Setter List of your ListBox Style:

<Style TargetType="local:MyListBox">
        <Setter Property="ItemTemplate" Value="{StaticResource MyItemTemplate}"/>^

Now it is your default template.

But do you need to add any specific behaviour to your ListBox, because you want to inherit from it. If you just want to add the specific item template, i would not recommend to derive from ListBox (in fact, the DataTemplate is not generic, it is always specific for a DataType). If you don't add specific behaviour I would go for creating a global DataTemplate (maybe defined in your app.xaml) and reference it as DataTemplate everytime you need it or I would create a specific style with this DataTemplate and set the style to the common ListBox.

If you have any questions, just leave a comment.

Hope this helps!

BR,

TJ

Answer 2

Other way to doit, if you want that your control looks by default as a ListBox. Just create a class derived from ListBox, and on the default constructor modify the DefaultStyleKey:

public class MyListBox : ListBox
{
    public MyListBox()
    {
        // the control would look like a listBox by default
        DefaultStyleKey = typeof (ListBox);
    }

    (...)
}