TabControl中的WPF UserControl仅实例化一次

Question

我有一个TabControl，其项目是ViewModel，是动态填充的。此外，还有一个UserControl链接到DataTemplate中的ViewModel。一切正常，显示效果很好。但是，SecurityRoleControl的构造函数只创建一次，无论有多少个选项卡。我需要在构建UserControl期间添加处理逻辑，但问题是它只在应用程序中调用一次。有人可以告诉我这种行为的原因，可能有任何解决方法吗？非常感谢。提前谢谢。

// MainWindow.XAML code
<TabControl
  IsSynchronizedWithCurrentItem="True"
  ItemsSource="{Binding ElementName=AdminMainWindow, Path=Workspaces}"
  ItemTemplate="{StaticResource ClosableTabItemTemplate}"
  Margin="4">
</TabControl>

// Data Template in Dictionary
<DataTemplate x:Key="ClosableTabItemTemplate">
  <DockPanel Width="120">
    <Button 
        Command="{Binding Path=CloseCommand}"
        Content="X"
        Cursor="Hand"
        DockPanel.Dock="Right"
        Focusable="False"
        FontFamily="Courier" 
        FontSize="9"
        FontWeight="Bold"  
        Margin="0,1,0,0"
        Padding="0"
        VerticalContentAlignment="Bottom"
        Width="16" Height="16" />
    <ContentPresenter 
        Content="{Binding Path=DisplayName}" 
        VerticalAlignment="Center" />
  </DockPanel>
</DataTemplate>

// Binding of ViewModel to UserControl
<DataTemplate DataType="{x:Type vm:SecurityRoleViewModel}">
  <uc:SecurityRoleControl />
</DataTemplate>

// Code to add a ViewModel to Workspace
SecurityRoleViewModel workspace = new SecurityRoleViewModel("Security Role Search");
workspace.MRN = viewModel.MRN;
workspaces.Add(workspace);
ICollectionView collectionView = CollectionViewSource.GetDefaultView(workspaces);
if (collectionView != null) {
  collectionView.MoveCurrentTo(workspace);
}

// Workspaces
public ObservableCollection<WorkspaceViewModel> Workspaces { get { return workspaces; } }

// Constructor of SecurityRoleControl, which is called only once
public SecurityRoleControl() {
  InitializeComponent();
}