Wpf customcontrol how to bind button click inside itemscontrol DataTemplate

I have a custom control that inherits from Textbox, in .cs I have DependencyProperty SelectedItems (these items will appear inside the texbox if any) if the texbox doesn't look like a normal texbox.

In generic.xaml in Template I added new border and inside I put ItemsControl with item template like this

xaml itemControl:

<Border BorderBrush="Green" BorderThickness="1">
                        <ItemsControl x:Name="PART_SelectedItemsHost"
                                ItemsSource="{TemplateBinding SelectedItems}"
                                ItemTemplate="{TemplateBinding SelectedItemsTemplate}"
                                VerticalAlignment="Stretch"
                                HorizontalAlignment="Stretch"                                                                      
                                Margin="{TemplateBinding Padding}"
                                Visibility="Visible">
                            <ItemsControl.ItemsPanel>
                                <ItemsPanelTemplate>
                                    <WrapPanel IsItemsHost="True">
                                    </WrapPanel>
                                </ItemsPanelTemplate>
                            </ItemsControl.ItemsPanel>                               
                        </ItemsControl>                            
                    </Border>

      

        
        
        
      

    

Xaml ItemTemplate part:

<DataTemplate x:Key="DefaultSelectedItemsTemplate" >
    <Border x:Name="selectedItemBorder" BorderBrush="Gray" BorderThickness="1" CornerRadius="5" Background="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" Margin="5,1,1,1">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="15"/>
            </Grid.ColumnDefinitions>
            <TextBlock Grid.Column="0" Text="{Binding}" Margin="5,0,3,0"></TextBlock>
            <Button BorderThickness="0" Grid.Column="1" Click="???" or Command="???" >X</Button>
        </Grid>
    </Border>
</DataTemplate>

      

        
        
        
      

    

Now how can I bind this "X" button in my .cs file. I am trying to do this by overriding the OnApplyTemplate () method ... and I was able to bind the mousedown when I click on the texbox element, but I don’t know how to attach this click on the button

my.cs part

            public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();
        ItemsControl itmControl = GetTemplateChild("PART_SelectedItemsHost") as ItemsControl;

        if (itmControl != null)
        {
            itmControl.MouseLeftButtonDown += new MouseButtonEventHandler(itmControl_MouseLeftButtonDown);

            // blind click on X buttons in ItemsControl
        }

    }

    private void itmControl_MouseLeftButtonDown(object obj, MouseButtonEventArgs e)
    {
        //IsMouseLeftButtonDown = true;
        System.Diagnostics.Debug.WriteLine(e.OriginalSource.ToString());
        object item = (e.OriginalSource as FrameworkElement).DataContext;
        deleteSelectedItem(item);

    }

      

        
        
        
      

    

and here is a picture of how this control looks like ant so that the X button removes the item from the SelectedItem collection.

picture