Dependency property binding Issue WPF

Question

Kindly let me know what I am doing wrong

XAML of UserControl where I use my child UserControl with dependency property

ComboBox SelectedItem will Update SelectedEmployee,

This SelectedEmployee is further Binded with My child Control CardView:uEmployeeCard ViewModel Property

<ComboBox  Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="2"
           Style="{StaticResource UiComboBox}"
           ItemsSource="{Binding TB_EMPLOYEEList}"
           SelectedItem="{Binding SelectedEmployee,
                          Mode=TwoWay,
                          UpdateSourceTrigger=PropertyChanged}"
           SelectedValuePath="ID"
           SelectedValue="{Binding CurrentTB_RECIEPT.REFRENCEID}"
           ItemTemplate="{StaticResource ComboEmployeeTemplate}"/>

<CardView:uEmployeeCard  ViewModel="{Binding Path=SelectedEmployee}"
                         Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" 
                         Grid.RowSpan="3" VerticalAlignment="Top"/>

---

Dependency Property Code, Code Behind file of uEmployeeCard:

public  uEmployeeCard()
{
    InitializeComponent();
    this.DataContext = this;
}

public static readonly DependencyProperty ViewModelProperty = 
    DependencyProperty.Register("ViewModel",
        typeof(TB_EMPLOYEE),
        typeof(uEmployeeCard), new FrameworkPropertyMetadata
            {
                BindsTwoWayByDefault = true,
                DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged
            });

[Bindable(true)]
public  TB_EMPLOYEE ViewModel
{
    get { return (TB_EMPLOYEE)GetValue(ViewModelProperty); } //do NOT modify anything in here
    set { SetValue(ViewModelProperty, value);  } //...or here
}

---

Xaml File of uEmployeeCard (Child User Control):

<StackPanel Grid.Column="0" Grid.Row="0" Orientation="Horizontal">
    <TextBlock Style="{StaticResource UiTextBlock}"
               Text="{Binding Path=ViewModel.TITLE}"/>
    <TextBlock Style="{StaticResource UiTextBlock}"
               Text="{Binding Path=ViewModel.FIRSTNAME}"/>
    <TextBlock Style="{StaticResource UiTextBlock}"
               Text="{Binding Path=ViewModel.FIRSTNAME}"/>
</StackPanel>
<StackPanel Grid.Column="0" Grid.Row="1" Orientation="Vertical" Grid.RowSpan="2">
    <TextBlock Style="{StaticResource UiTextBlock}"
               Text="{Binding Path=ViewModel.NATNO}"/>
</StackPanel>

---

I put breakpoint to check whether the dependency property get affected on update from ComboBox on parent user control. but not...

Answer 1

Have you already tried to edit the PropertyBinding in the ChildControl with the following:

"Mode=TwoWay, UpdateSourceTrigger=PropertyChanged"

You could also try to give your ComboBox a name and bind your ChildControl to it:

ViewModel="{Binding ElementName=NamedComboBox, Path=SelectedItem}"