[UWP] [VB] x：绑定到textBox.TextChanged工作，而textBox.TextChanging不 [英] [UWP][VB] x:Bind to textBox.TextChanged Works While textBox.TextChanging Does Not

问题描述

大家好，

我将网格视图中的文本框绑定（x：绑定）到ObservableCollection中的某些数据。 文本框包含我必须验证的各种数字数据（正整数，sbyte，double等） 当我x：将每个文本框绑定到一个用于TextChanging事件的事件处理程序
并验证它时，它会编译但我得到一个JIT未处理的win32异常。 但是，如果我x：绑定到TextChanged事件，它工作正常（虽然textchanged事件给出了不理想的视觉性能 - 不正确的字符
暂时可见）。 有谁知道为什么TextChanging事件会导致异常？

这是每个场景的相关XAML和代码;我的代码中唯一的差异如下所示：

TextChanged（工作）：

< TextBox Text =" {x：Bind Value，Mode = TwoWay}" TextChanged =" {x：Bind textBox_TextChanged}" Name =" {x：Bind Name，Mode = OneTime}"宽度="95" Margin =" 0,0,0,0" /> 

和事件处理程序签名：

 Public Sub textBox_TextChanged（sender As Object，e As TextChangedEventArgs）
'验证码
 End Sub 

TextChanging（不起作用） ）：

< TextBox Text =" {x：Bind Value，Mode = TwoWay}" TextChanging =" {x：Bind textBox_TextChanging}" Name =" {x：Bind Name，Mode = OneTime}"宽度="95" Margin =" 0,0,0,0" /> 

eventhandler签名：

 Public Sub textBox_TextChanging（sender as Object，e As TextBoxTextChangingEventArgs）
'验证码
 End Sub 

添加代码：

xaml：

< Grid Background =" {ThemeResource ApplicationPageBackgroundThemeBrush}"> 
< GridView ItemsSource =" {Binding}"余量= QUOT; 0,0,200,150" > 
 
< GridView.ItemTemplate> 
< DataTemplate x：DataType =" local：MyData"> 
 
< StackPanel Orientation =" Horizo​​ntal" > 
< TextBlock Text =" {x：Bind DataName，Mode = OneWay}"宽度="500" TextAlignment = QUOT;右" /> 
< TextBox Text =" {x：Bind Value，Mode = TwoWay}" TextChanging =" {Binding textBox_TextChanging}"宽度="95" /> 
 
< / StackPanel> 
 
< / DataTemplate> 
< /GridView.ItemTemplate> 
 
< / GridView> 
 
< / Grid> 

VB：

 Public NotInheritable Class MainPage 
 Inherits Page 
 Public Sub New（）
 InitializeComponent（）
 DataContext = MyData.LoadFromDictionaryToObservableCollection 
 End Sub 
 
结束类
 
公共类MyData 
实现INotifyPropertyChanged 
公共事件PropertyChanged As PropertyChangedEventHandler 
私有事件INotifyPropertyChanged_PropertyChanged As PropertyChangedEventHandler实现INotifyPropertyChanged.PropertyChanged 
 
 Dim Local_DataContainer As Windows.Storage.ApplicationDataContainer = Windows.Storage.ApplicationData.Current.LocalSettings 
 
 Private _Value As String 
 Private _Type As DataType 
 Private _DataName As String 
 Public Sub New（DataName As String，Value As String，Type As DataType）
 _DataName = DataName 
 _Value = Value 
 _Type = Type 
 End Sub 
公共共享函数LoadFromDictionaryToObservableCollection（）As ObservableCollection（Of MyData）
 Dim CurrentCollection As New ObservableCollection（Of MyData）
 CurrentCollection .Add（New MyData（" Item1"，" 65.2"，DataType._Double））
 CurrentCollection.Add（New MyData（" Item2"，" 15"，DataType._Byte））
 CurrentCollection.Add（New MyData（" Item3"，" 855"，DataType._Integer））
返回CurrentCollection 
结束函数
 Public Enum DataType 
 _Byte 
 _Double 
 _Integer 
 End Enum 
 
 Public ReadOnly Property DataName（）As String 
 Get 
 Return _DataName 
 End Get 
 
结束物业
公共物业价值（）作为字符串
获取
返回_Value 
结束获取
设置
 _Value = Value 
 RaisePropertyChanged（）
 SaveData（Me.DataName，Me.Value）
 
结束集
结束物业
公开ReadOnly Property Type（）As DataType 
 Get 
 Return _Type 
 End Get 
 
 End Property 
 
 Private Sub SaveData（DataName As String， DataValue As String）
 Local_DataContainer.Values（DataName）= DataValue 
 End Sub 
 
 Private Sub RaisePropertyChanged（< CallerMemberName>可选调用者As String =""）
 RaiseEvent PropertyChanged（Me，New PropertyChangedEventArgs（caller））
 End Sub 
 Public Sub textBox_TextChanging（sender as Object，e As TextBoxTextChangingEventArgs）'处理textBox .TextChanging 
'验证数据
结束Sub 
 Public Sub textBox_TextChanged（sender As Object，e As TextChangedEventArgs）'Handles textBox.TextChanging 
'验证数据
 End Sub 
结束等级

解决方案

嗨rTolder，

在这种情况下，您需要使用绑定而不是x：bind。对于绑定，它具有UpdateSourceTrigger，这意味着例如当文本框的文本发生更改时，它可以立即更新数据源。但是对于x：bind，不支持UpdateSourceTrigger。
有关详细信息，请参阅
数据绑定深度 。在文章的底部，有一个比较绑定和x：bind。

最好的问候，

Neal Wang

Hi All,

I'm binding (x:Bind) textBoxes in a gridview to some data in an ObservableCollection.  The textboxes contain a variety of numeric data that I have to validate (positive integers, sbyte, double, etc.)  When I x:Bind each textbox to an eventhandler for the TextChanging event and to validate it, it compiles but I get a JIT unhandled win32 exception.  However, if I x:Bind to the TextChanged event, it works fine (though the textchanged event gives suboptimal visual performance -- incorrect characters are momentarily visible).  Does anyone know why the TextChanging event would result in an exception?

Here is the relevant XAML and code behind for each scenario; the only differences in my code are shown below:

TextChanged (works):

<TextBox Text = "{x:Bind Value, Mode = TwoWay}" TextChanged="{x:Bind textBox_TextChanged}" Name="{x:Bind Name , Mode = OneTime  }" Width = "95" Margin = "0,0,0,0"  />

and the eventhandler signature:

Public Sub textBox_TextChanged(sender As Object, e As TextChangedEventArgs) 
               '  Validation Code
End Sub

TextChanging (does not work):

<TextBox Text = "{x:Bind Value, Mode = TwoWay}" TextChanging="{x:Bind textBox_TextChanging}" Name="{x:Bind Name , Mode = OneTime  }" Width = "95" Margin = "0,0,0,0"  />

eventhandler signature:

 Public Sub textBox_TextChanging(sender As Object, e As TextBoxTextChangingEventArgs) 
        '  Validation Code
End Sub

Added Code:

xaml:

<Grid Background = "{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <GridView ItemsSource = "{Binding}" Margin="0,0,200,150" >

            <GridView.ItemTemplate>
                <DataTemplate x:DataType = "local:MyData">

                    <StackPanel Orientation = "Horizontal" >
                        <TextBlock Text = "{x:Bind DataName , Mode = OneWay }" Width = "500" TextAlignment="Right"  />
                        <TextBox Text = "{x:Bind Value, Mode = TwoWay}" TextChanging="{Binding textBox_TextChanging}"  Width = "95"  />
           
                    </StackPanel>

                </DataTemplate>
            </GridView.ItemTemplate>

        </GridView>
  
    </Grid>

VB:

Public NotInheritable Class MainPage
    Inherits Page
    Public Sub New()
        InitializeComponent()
        DataContext = MyData.LoadFromDictionaryToObservableCollection
    End Sub

End Class

Public Class MyData
    Implements INotifyPropertyChanged
    Public Event PropertyChanged As PropertyChangedEventHandler
    Private Event INotifyPropertyChanged_PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

    Dim Local_DataContainer As Windows.Storage.ApplicationDataContainer = Windows.Storage.ApplicationData.Current.LocalSettings

    Private _Value As String
    Private _Type As DataType
    Private _DataName As String
    Public Sub New(DataName As String, Value As String, Type As DataType)
        _DataName = DataName
        _Value = Value
        _Type = Type
    End Sub
    Public Shared Function LoadFromDictionaryToObservableCollection() As ObservableCollection(Of MyData)
        Dim CurrentCollection As New ObservableCollection(Of MyData)
        CurrentCollection.Add(New MyData("Item1", "65.2", DataType._Double))
        CurrentCollection.Add(New MyData("Item2", "15", DataType._Byte))
        CurrentCollection.Add(New MyData("Item3", "855", DataType._Integer))
        Return CurrentCollection
    End Function
    Public Enum DataType
        _Byte
        _Double
        _Integer
    End Enum

    Public ReadOnly Property DataName() As String
        Get
            Return _DataName
        End Get

    End Property
    Public Property Value() As String
        Get
            Return _Value
        End Get
        Set
            _Value = Value
            RaisePropertyChanged()
            SaveData(Me.DataName, Me.Value)

        End Set
    End Property
    Public ReadOnly Property Type() As DataType
        Get
            Return _Type
        End Get

    End Property

    Private Sub SaveData(DataName As String, DataValue As String)
        Local_DataContainer.Values(DataName) = DataValue
    End Sub

    Private Sub RaisePropertyChanged(<CallerMemberName> Optional caller As String = "")
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(caller))
    End Sub
    Public Sub textBox_TextChanging(sender As Object, e As TextBoxTextChangingEventArgs) 'Handles textBox.TextChanging
        'validate data
    End Sub
    Public Sub textBox_TextChanged(sender As Object, e As TextChangedEventArgs) 'Handles textBox.TextChanging
        'validate data
    End Sub
End Class

解决方案

Hi rTolder,

In this situation , you need to use binding instead of x:bind. For binding, it has UpdateSourceTrigger, which means for example when the text of Textbox changes, it can update the data source immediately. However for x:bind, UpdateSourceTrigger is not supported. For more information , you can refer to Data binding in depth. In the bottom of the article, there is a comparison between binding and x:bind.

Best Regards,

Neal Wang

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