像这样：

问题是当我在项目中添加一个项目时,ContentControl没有更新和更改DataTemplate,我尝试设置模式,UpdateSourceTrigger等,但失败了.在viewmodel中,删除一个项目后,我使用这个语句,它将很好地工作< 1>：

private void ExecuteDeleteClientCommand()
{
    ...
    if (DeleteClient(item))
    {
        ObservableCollection<Myviewmodel> tmp = TabItems;
        TabItems = null;
        TabItems = tmp;
    }
}

.

<ContentControl 
    ContentTemplateSelector="{StaticResource MyDataTemplateSelector}" 
    Content="{Binding Items}"/>

.

public class SingleClientDataTemplateSelector : DataTemplateSelector
{
    public override DataTemplate SelectTemplate(object item,DependencyObject container)
    {
        ObservableCollection<Myviewmodel> obj = 
            item as ObservableCollection<Myviewmodel>;
        if (null == obj || 0 == obj.Count)
        {
            return App.Current.FindResource("NullItemDataTemplate") as DataTemplate;
        }
        return App.Current.FindResource("DefaultDataTemplate") as DataTemplate;
    }
}

编辑：
使用这种方式删除一项后也失败：

RaisePropertyChanging(ItemsPropertyName);
RaisePropertyChanged(ItemsPropertyName);

但我想知道为什么它适用于< 1>.

Edited2
这是蜕变：

public const string ItemsPropertyName = "Items";
private ObservableCollection<Myviewmodel> items = new ObservableCollection<Myviewmodel>();
public ObservableCollection<SingleClientDetailviewmodel> TabItems
{
    get { return items; }
    set 
    { 
        if (items == value) { return;}
        RaisePropertyChanging(ItemsPropertyName);
    items = value;
    RaisePropertyChanged(ItemsPropertyName);
    }
}