改变一个 <Type> 列表框背景色

Question

I have a Listbox that holds a list of type customer. So my Listbox.Items is not of type ListItem anymore, it is of type customer.

I have an isActive flag in the customer field and I was wondering how I would set the back color say to red, if the isActive is true.

Currently I have tried this but it doesnt work since I can't cast Customers to type ListBoxtem

            List<object> inactiveCustomers = new List<object>();
        foreach (Customer item in ListBoxCustomers.Items)
        {
            if (!item.IsActive)
            {
                inactiveCustomers.Add(item);
                int index = ListBoxCustomers.Items.IndexOf(item);
                ListBoxItem x = (ListBoxItem)ListBoxCustomers.Items[index];
                x.Background = Brushes.Red;
            }
        }

EDIT: I am calling a method that does the above code whenever I deselect a checkbox that is for active customers. Whenever I deselect the Active Checkbox, I iterate through the customers and display all of them, and at this time, I would like to change the backcolor of the inactive to distinguish which ones are inactve/active

Answer 1

There are two ways to do this. The "correct" WPF way is to do it all in XAML:

<ListBox x:Name="ListBoxCustomers" ItemsSource="{Binding Customers}">
    <ListBox.ItemContainerStyle>
        <Style TargetType="ListBoxItem">
            <Style.Triggers>
                <DataTrigger Binding="{Binding IsActive}" Value="False">
                    <Setter Property="Background" Value="Red" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

The WinForms-style way to do this in code-behind requires getting the container from the listbox. However, due to UI virtualization, not all items necessary have a container. Therefore, this code will only change the containers for the the current visible items. If the ListBox is scrolled, the new items may or may not have the setting you expect (depending on recycling rules).

List<object> inactiveCustomers = new List<object>();
foreach (Customer item in ListBoxCustomers.Items)
{
    if (!item.IsActive)
    {
        inactiveCustomers.Add(item);
        var container =  ListBoxCustomers.ItemContainerGenerator.ContainerFromItem(item) as ListBoxItem;
        if (container != null)
            container.Background = Brushes.Red;
    }
}

Answer 2

To get the ListBoxItem you can use the ListBox 's ItemContainerGenerator . Make sure you do this after loading has completed, like in a Loaded event handler, since the controls don't exist yet before loading.

void Window_Loaded(object sender, RoutedEventArgs e)
{
    List<object> inactiveCustomers = new List<object>();
    foreach (Customer item in ListBoxCustomers.Items)
    {
        if (!item.IsActive)
        {
            inactiveCustomers.Add(item);
            ListBoxItem x = ListBoxCustomers.ItemContainerGenerator.ContainerFromItem(item) as ListBoxItem;
            if (x != null)
                x.Background = Brushes.Red;
        }
    }
}