數據綁定不能在WPF中使用VB.NET

Question

我一直在嘗試獲取數據綁定的句柄，並且遇到了麻煩使其工作。有人能指引我朝着正確的方向嗎？

我使用VS2012並在WPF/vb.net中編程。我有一個xaml UI，一個更新屬性的類，以及運行我的主循環的模塊。我試圖根據模塊中的動態數據更新UI中的文本塊。

下面是從UI的重要XAML：

<Page x:Class="pPage" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:local="clr-namespace:BMI_WPF_v1" 
    mc:Ignorable="d" 
    Title="BMI"> 

<Page.Resources> 
    <local:clsItemGUI x:Key="clsitemgui" /> 
</Page.Resources> 

<TextBlock x:FieldModifier="public" x:Name="p_force" Text="{Binding Path=Force, UpdateSourceTrigger=PropertyChanged}" /> 

這裏是我打電話給我的主模塊中嘗試更新GUI：

Dim bmiUI As New clsItemGUI 
bmiUI.UpdateForce(currentForce) 

這裏還有一個，就是類更新GUI：

Imports System.Collections.ObjectModel 
Imports System.ComponentModel 

Public Class clsItemGUI 
Implements INotifyPropertyChanged 

Private ForceValue As Double 

Sub New() 
End Sub 

Public Sub UpdateForce(ByVal inputForce As String) 
    Me.ForceValue = inputForce 
End Sub 

Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged 

Public Property Force() As Double 
    Get 
     Return ForceValue 
    End Get 
    Set(ByVal value As Double) 
     ForceValue = value 
     OnPropertyChanged("Force") 
    End Set 
End Property 

Protected Sub OnPropertyChanged(ByVal name As String) 
    RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(name)) 
End Sub 

End Class 

它看起來像我更新ForceValue，但這不是觸發UI上的更新。顯然我錯過了一些愚蠢的東西，但是我還沒有找到合適的資源。

Answer 1

試試這個

添加的datacontext下頁資源

<Page.DataContext> 

    <local:clsItemGUI/> 

</Page.DataContext> 

（與模式=雙向）

<TextBlock x:FieldModifier="public" x:Name="p_force" Text="{Binding Path=Force, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" /> 

Answer 2

您必須指定DataContext根佈局（在我的例子是Grid）：

<Grid DataContext="{StaticResource clsitemgui}"> 
    <Grid.RowDefinitions> 
     <RowDefinition Height="30" /> 
     <RowDefinition Height="30" /> 
    </Grid.RowDefinitions> 

    <TextBlock x:FieldModifier="public" x:Name="p_force" Text="{Binding Path=Force, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" /> 
    <Button x:Name="btn" Grid.Row="1" Content="Change" Click="Button_Click" />   
</Grid> 

，或者你可以設置Source屬性，當你綁定，就像這樣：

<TextBlock x:FieldModifier="public" x:Name="p_force" Text="{Binding Path=Force, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" /> 

你也有錯誤UpdateForce方法，你應該不分配新值Force財產ForceValue領域。當您將此值分配給字段OnPropertyChanged時，它不會被調用。

Public Class clsItemGUI 
    Implements INotifyPropertyChanged 

    Private ForceValue As Double 

    Sub New() 
     Force = 2.5 
    End Sub 

    Public Sub UpdateForce(ByVal inputForce As Double) 
     Me.Force = inputForce 
    End Sub 

    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged 

    Public Property Force() As Double 
     Get 
      Return ForceValue 
     End Get 
     Set(ByVal value As Double) 
      ForceValue = value 
      OnPropertyChanged("Force") 
     End Set 
    End Property 

    Protected Sub OnPropertyChanged(ByVal name As String) 
     RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(name)) 
    End Sub 

End Class 

當你更新你應該做的，你分配爲DataContext所以你應該施放此對象，並對其調用UpdateForce功能對當前對象：

Private Sub Button_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) 
    Dim dt As clsItemGUI 
    dt = CType(btn.DataContext, clsItemGUI) 
    dt.UpdateForce(5.2) 
End Sub