problem with Custom ComboBox not raising notification changes during SelectedItem change

Question

Hi, in my wpf C# .net 8 application i have a custom Control composed of a Label and ComboBox, the problem i am experiencing is that the Custom Control's ComboBox doesn't raise the SelectedItem change in the ViewModel, then i decided to test it with a normal wpf ComboBox and the notification was raised successfully, What can be the problem? Help fix the problem.

Here is the repos of this sample and Here is the Database i Used.

The two ComboBoxes you see use the same bindings and codes.

Answer 1

TemplateBinding can receive only oneway from template parent.

<Style TargetType="{x:Type local:FloatingLabelComboBox}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type local:FloatingLabelComboBox}">
                <StackPanel FlowDirection="LeftToRight">
                    <Label Content="{TemplateBinding LabelText}"
                        Foreground="{TemplateBinding LabelForeground}"
                        FontSize="{TemplateBinding LabelFontSize}"
                        VerticalAlignment="Stretch"
                        Margin="-5 0 0 0" 
                />

                    <ComboBox x:Name="comboBox"
                            ItemsSource="{TemplateBinding ComboBoxItemsSource}"
                            SelectedItem="{Binding ComboBoxSelectedItem,RelativeSource={RelativeSource  Mode=TemplatedParent},Mode=TwoWay}"
                            SelectedValuePath="{TemplateBinding ComboBoxSelectedValuePath}"
                            SelectedValue="{Binding ComboBoxSelectedValue,RelativeSource={RelativeSource  Mode=TemplatedParent},Mode=TwoWay}"
                            DisplayMemberPath="{TemplateBinding ComboBoxDisplayMemberPath}"
                            HorizontalAlignment="Stretch"
                            VerticalAlignment="Center"
                            Width="Auto"
                            Height="Auto"
                            materialdesign:HintAssist.IsFloating="False"
                            materialdesign:ColorZoneAssist.Mode="Dark"
                            materialdesign:HintAssist.HintOpacity="0.10"
                            materialdesign:HintAssist.FontFamily="Century Gothic"
                            Foreground="{TemplateBinding ComboBoxForeground}">

                    </ComboBox>
                </StackPanel>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>