我創建了一個帶有TextBlock的窗口。我綁定了Text屬性,一切正常。 但是 當我在一個任務內改變有界屬性時,沒有任何工作!綁定和異步操作
你知道爲什麼嗎?
Public Async Sub StartProgress()
Try
LoadingText = "text 1" 'Works perfect
Dim fResult As Boolean = Await LoadModules()
If Not fResult Then
MessageBox.Show(Me.Error)
End If
m_oView.Close()
Catch ex As Exception
Msg_Err(ex)
End Try
End Sub
Public Async Function LoadModules() As Task(Of Boolean)
Try
Await Task.Delay(3000)
LoadingText = "text 2" 'Nothing Happens
Await Task.Delay(5000)
LoadingText = "complete" 'Nothing Happens
Await Task.Delay(3000)
Return True
Catch ex As Exception
Me.Error = ex.Message
Return False
End Try
End Function
文本2和3從不顯示。如果我動態改變textblcok(例如:m_oView.txtLoadingText.Text)的文本,它工作正常(但它是mnot的解決方案)
編輯 這是視圖模型基地,每個視圖模型實現了類。
Public Class VM_Base
Implements IDisposable
Implements INotifyPropertyChanged
Private m_oDS As MxDataSet
Public Property [Error] As String
Public Event PropertyChanged As PropertyChangedEventHandler _
Implements INotifyPropertyChanged.PropertyChanged
Protected Sub New()
m_oDS = New MxDataSet
End Sub
Protected Overrides Sub Finalize()
Try
Me.Dispose(False)
Debug.Fail("Dispose not called on ViewModel class.")
Finally
MyBase.Finalize()
End Try
End Sub
Public Sub Dispose() Implements IDisposable.Dispose
Me.Dispose(True)
GC.SuppressFinalize(Me)
End Sub
Protected Overridable Sub Dispose(disposing As Boolean)
End Sub
Protected Overridable Sub OnPropertyChanged(propertyName As String)
Me.EnsureProperty(propertyName)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
<Conditional("DEBUG")> _
Private Sub EnsureProperty(propertyName As String)
If TypeDescriptor.GetProperties(Me)(propertyName) Is Nothing Then
Throw New ArgumentException("Property does not exist.", "propertyName")
End If
End Sub
End Class
StartProgress怎麼叫:
<i:Interaction.Triggers>
<i:EventTrigger EventName="ContentRendered">
<i:InvokeCommandAction Command="{Binding DataContext.WindowsActivatedCommand,ElementName=fLoading}" />
</i:EventTrigger>
</i:Interaction.Triggers>
編輯 綁定TextBlock的物業
Public Property LoadingText As String
Get
Return m_sLoadingText
End Get
Set(value As String)
m_sLoadingText = value
OnPropertyChanged("LoadingText")
End Set
End Property
<TextBlock x:Name="txtLoading" Width="450"
Grid.Row="1" VerticalAlignment="Center"
HorizontalAlignment="Left"
TextWrapping="Wrap" Text="{Binding LoadingText}">
</TextBlock>
我沒有任何錯誤,當我嘗試設置文本屬性的構造函數。此外,我使用Task,無論是Dispatcher還是BackgroundWorker,以關注調用UI。另外,如果我強制TextBlock更改文本,例如m_oView.txtLoadingText.Text =「something」,那麼它會改變! –