我创建了一个带有TextBlock的窗口。我绑定了Text属性,一切正常。 但是 当我在一个任务内改变有界属性时,没有任何工作!绑定和异步操作
你知道为什么吗?
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从不显示。如果我动态改变textblcok(例如:m_oView.txtLoadingText.Text)的文本,它工作正常(但它是mnot的解决方案)
编辑 这是视图模型基地,每个视图模型实现了类。
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怎么叫:
<i:Interaction.Triggers>
<i:EventTrigger EventName="ContentRendered">
<i:InvokeCommandAction Command="{Binding DataContext.WindowsActivatedCommand,ElementName=fLoading}" />
</i:EventTrigger>
</i:Interaction.Triggers>
编辑 绑定TextBlock的物业
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>
我没有任何错误,当我尝试设置文本属性的构造函数。此外,我使用Task,无论是Dispatcher还是BackgroundWorker,以关注调用UI。另外,如果我强制TextBlock更改文本,例如m_oView.txtLoadingText.Text =“something”,那么它会改变! –