Question

我创建了一个简单的数据网格来显示一些值，让用户更改它们并回读后台程序中更改的值。这是XAML设计文件

<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
    <Button x:Name="ButAdd" Content="Add Row" HorizontalAlignment="Left" Height="23" Margin="362,34,0,0" VerticalAlignment="Top" Width="77"/>
    <TextBox x:Name="TeBoResult" HorizontalAlignment="Left" Height="90" Margin="52,220,0,0" TextWrapping="Wrap" Text="Display the Row 0 colmn 1 changed value here:" VerticalAlignment="Top" Width="322" AcceptsReturn="True" IsManipulationEnabled="True"/>
    <Button x:Name="ButRead" Content="Read Row 2" HorizontalAlignment="Left" Height="24" Margin="425,184,0,0" VerticalAlignment="Top" Width="82"/>
    <DataGrid x:Name="DaGr" ItemsSource="{Binding}" HorizontalAlignment="Left" Height="133" Margin="10,75,0,0" VerticalAlignment="Top" Width="174" AutoGenerateColumns="False" IsManipulationEnabled="True" EnableColumnVirtualization="True" >
        <DataGrid.Columns>
            <DataGridTextColumn Header="Text" Binding="{Binding Path=No, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
            <DataGridCheckBoxColumn Header="Check box" Binding="{Binding Path=Sel}"/>
            <DataGridComboBoxColumn Header="Combo box" Binding.XmlNamespaceManager="{Binding Path=Drop}"/>
        </DataGrid.Columns>
    </DataGrid>
    <ComboBox x:Name="CoBo_IN" HorizontalAlignment="Left" Height="20" Margin="344,100,0,0" VerticalAlignment="Top" Width="84" Visibility="Visible">
        <ComboBoxItem Content="Move" HorizontalAlignment="Left" Width="88"/>
        <ComboBoxItem Content="Dock" HorizontalAlignment="Left" Width="88" Selected="ComboBoxItem_Selected"/>
    </ComboBox>
</Grid>

背景vb.net代码在这里

Imports System.Collections.ObjectModel
Imports System.ComponentModel
Imports System.Runtime.CompilerServices
Imports DataGrid.datset
Imports System.Windows
Class MainWindow
    Public Property coll As New ObservableCollection(Of bind)()
    Private Sub ButAdd_Click(sender As Object, e As RoutedEventArgs) Handles ButAdd.Click
       Dim qw As New bind()
       qw.No = "Change Me"
       qw.Sel = Nothing
       qw.Drop = CoBo_IN
       coll.Add(qw)
       DaGr.ItemsSource = coll
    End Sub

   Private Sub ButRead_Click(sender As Object, e As RoutedEventArgs) Handles ButRead.Click
        Dim val As String
        For Each item As bind In DaGr.Items
            val = item.No
            TeBoResult.Text = TeBoResult.Text & val
        Next
   End Sub

End Class

Public Class datset : Implements INotifyPropertyChanged
   Public Event PropertyChanged As PropertyChangedEventHandler _
   Implements INotifyPropertyChanged.PropertyChanged


   Private Sub NotifyPropertyChanged(<CallerMemberName()> Optional ByVal propertyName As String = Nothing)
       RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
   End Sub

   Public Structure bind
       Public Property No As String
       Public Property Sel As Boolean
       Public Property Drop As ComboBox
   End Structure

End Class

所以当我点击Add Row按钮时，带有默认内容的行会被添加到TextColumn和CheckBoxColumn中，但是ComboBoxColumn dosent会显示组合!!（但是当我在这个单元格内双击时，ComboBox会出现，但它是空的）。这种行为可能是什么原因？

接下来，用户将更改TextColumn中的内容，并根据需要在GUI中进行更改。

接下来，当用户单击botton Read Row时，TextColumn的所有内容将依次读取并显示在Result文本框中。问题是，当GUI按顺序读取时有一个新文本， val 变量仍然只显示以前绑定的值。我认为问题在于TwoWay绑定，但它似乎是另一回事。

为什么 DataGrid 上的读取不会给出更新值？

Answer 1

我不太了解VB，但我可以看到这里有些东西不行。例如ItemsSource="{Binding}"。在这里，您必须引用要绑定的集合，在本例中为coll。代码应该是这样的：

<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525"
x:Name="window">
<Grid>
    <Button x:Name="ButAdd" Content="Add Row" HorizontalAlignment="Left" Height="23" Margin="362,34,0,0" VerticalAlignment="Top" Width="77"/>
    <TextBox x:Name="TeBoResult" HorizontalAlignment="Left" Height="90" Margin="52,220,0,0" TextWrapping="Wrap" Text="Display the Row 0 colmn 1 changed value here:" VerticalAlignment="Top" Width="322" AcceptsReturn="True" IsManipulationEnabled="True"/>
    <Button x:Name="ButRead" Content="Read Row 2" HorizontalAlignment="Left" Height="24" Margin="425,184,0,0" VerticalAlignment="Top" Width="82"/>
    <DataGrid x:Name="DaGr" ItemsSource="{Binding col, ElementName =window}" HorizontalAlignment="Left" Height="133" Margin="10,75,0,0" VerticalAlignment="Top" Width="174" AutoGenerateColumns="False" IsManipulationEnabled="True" EnableColumnVirtualization="True" >
        <DataGrid.Columns>
            <DataGridTextColumn Header="Text" Binding="{Binding Path=No, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
            <DataGridCheckBoxColumn Header="Check box" Binding="{Binding Path=Sel, Mode=TwoWay}"/>
            <DataGridComboBoxColumn Header="Combo box" Binding.XmlNamespaceManager="{Binding Path=Drop, Mode=TwoWay"/>
        </DataGrid.Columns>
    </DataGrid>
    <ComboBox x:Name="CoBo_IN" HorizontalAlignment="Left" Height="20" Margin="344,100,0,0" VerticalAlignment="Top" Width="84" Visibility="Visible">
        <ComboBoxItem Content="Move" HorizontalAlignment="Left" Width="88"/>
        <ComboBoxItem Content="Dock" HorizontalAlignment="Left" Width="88" Selected="ComboBoxItem_Selected"/>
    </ComboBox>
</Grid>

注意项目源绑定和窗口名称，还要注意绑定应该是双向的，也用于更新源代码。这个新绑定引用了col集合。现在在他的代码背后，你不应该在每次添加项目时重新设置网格intems源。如果集合是一个可观察的集合，那么它会自动添加，现在这些项目应该可以工作::

Private Sub ButAdd_Click(sender As Object, e As RoutedEventArgs) Handles ButAdd.Click
   Dim qw As New bind()
   qw.No = "Change Me"
   qw.Sel = Nothing
   qw.Drop = CoBo_IN
   coll.Add(qw)
End Sub

从DataGrid读取不起作用

1 个答案: