ViewModel不会更新Combobox SelectedValue

Question

我在VSIX项目中遇到了一个Combobox问题。我正在使用MVVM模式。

<ComboBox
            ItemsSource="{Binding ProjectList, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
            DisplayMemberPath="Name"
           IsSynchronizedWithCurrentItem="True"
            Style="{StaticResource MyStyle}"
            SelectedValue="{Binding Project, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

这是我的Combobox，它是项目列表的bindet。 SelectedValue是列表的一个项目。像这样：

ProjectList = New List(Of Project)(Helper.GetFormsProjects())
  If ProjectList.Count > 0 Then
     Project = ProjectList(0)
  End If

但如果我在Combobox中选择另一个值，它就不会调用项目属性的setter。

以下是属性：

   Public Property _projectList As List(Of Project)
   Public Property ProjectList As List(Of Project)
      Get
         Return _projectList
      End Get
      Set(value As List(Of Project))
         _projectList = value
         OnPropertyChanged()
      End Set
   End Property

   Public Property _project As Project
   Public Property Project As Project
          Get
             Return _project
          End Get
          Set(value As Project)
             _project = value
             OnPropertyChanged()
          End Set
       End Property