我创建了一个窗口,里面有一个TextBlock。我绑定了Text属性,一切正常。
但是当我在Task中更改绑定的属性时,什么也不起作用!!
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从未显示。如果我动态更改文本块的文本(例如:m_oView.txtLoadingText.Text),它可以正常工作(但这不是解决方案)。
编辑 这是ViewModel Base,每个ViewModel都实现该类。
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方法是如何调用的:
<i:Interaction.Triggers>
<i:EventTrigger EventName="ContentRendered">
<i:InvokeCommandAction Command="{Binding DataContext.WindowsActivatedCommand,ElementName=fLoading}" />
</i:EventTrigger>
</i:Interaction.Triggers>
编辑 将TextBlock绑定到属性
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>