Why comboboxitem show strange blue blank even I rewrite it? - wpf

Question

I rewrite a ComboBoxItem by custom control with these code:
XAML:
<Style TargetType="{x:Type local:SComboBoxItem}">
<Setter Property="Padding" Value="5,15"></Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type local:SComboBoxItem}">
<Border Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}" Cursor="{TemplateBinding Cursor}" >
<Label Foreground="{TemplateBinding Foreground}" Margin="{TemplateBinding Padding}" FontFamily="{TemplateBinding FontFamily}" FontSize="{TemplateBinding FontSize}" FontWeight="{TemplateBinding FontWeight}" Padding="0" Content="{TemplateBinding Content}">
</Label>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Background" Value="#dbdbdb"></Setter>
</Trigger>
<Trigger Property="IsSelected" Value="true">
<Setter Property="Background" Value="#c9c8c9"></Setter>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Code-behind:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace SealBase
{
public class SComboBoxItem : ComboBoxItem
{
static SComboBoxItem()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(SComboBoxItem), new FrameworkPropertyMetadata(typeof(SComboBoxItem)));
}
}
}
Well, and then I make a demo as this:
<ComboBox Grid.Column="1" Margin="10,10,0,10" HorizontalContentAlignment="Stretch" Name="FontFaimlyCB" Height="50" Width="250">
<Seal:SComboBoxItem>123</Seal:SComboBoxItem>
<Seal:SComboBoxItem>123</Seal:SComboBoxItem>
<Seal:SComboBoxItem>123</Seal:SComboBoxItem>
<Seal:SComboBoxItem>123</Seal:SComboBoxItem>
</ComboBox>
All is OK as below:
However, after I change the code of the demo as this:
<ComboBox Grid.Column="1" Margin="10,10,0,10" HorizontalContentAlignment="Stretch" Name="FontFaimlyCB" Height="50" Width="250" ItemsSource="{Binding Source={x:Static Fonts.SystemFontFamilies}}">
<ComboBox.ItemTemplate>
<DataTemplate>
<Seal:SListBoxItem Content="{Binding}">
</Seal:SListBoxItem>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
And now it turns out to be something wrong:
The demo occurs a strange blue blank. I don't know why it turns out to be this. I doubt it is the problem of the ComboBox control. But after I rewrite a brand new one inherits the ComboBox with the custom control. The problem still here.
What's wrong with this? And how can I solve it? Thank you.

Answer 1

What's wrong with this?
The element in the ItemTemplate automatically gets wrapped in a ComboBoxItem container.
And how can I solve it?
If you want to render a SListBoxItem for each item, you could create a custom ComboBox class that overrides the GetContainerForItemOverride() method:
public class CustomComboBox : ComboBox
{
protected override bool IsItemItsOwnContainerOverride(object item)
{
return (item is SListBoxItem);
}
protected override DependencyObject GetContainerForItemOverride()
{
return new SListBoxItem();
}
}