WPF组合框的SelectedItem动态绑定

我想一个组合框的的SelectedItem绑定到视图模型里面一个ObservableCollection的具体项目。WPF组合框的SelectedItem动态绑定

在视图模型我有一个的ObservableCollection属性：

Public Property SourceList As ObservableCollection(Of CustomItem)

然后，我有这两个自定义类

Public Class CustomItem 
    Public Property Code As String 
    Public Property Source As List(Of CustomValue) 
    Public Property Selection As Object 
End Class 

Public Class CustomValue 
    Public Property Id As Integer 
    Public Property Desc As String 
End Class

在XAML

<Border Tag="10"> 
    <ComboBox DisplayMemberPath="Desc"> 
      <ComboBox.ItemsSource> 
       <MultiBinding Converter="{StaticResource comboSourceConverter}"> 
        <Binding Path="SourceList"/> 
        <Binding Path="Tag" RelativeSource="{RelativeSource AncestorLevel=1, Mode=FindAncestor, AncestorType=Border}" /> 
       </MultiBinding> 
      </ComboBox.ItemsSource> 
     </ComboBox> 
</Border>

我使用该转换器的组合框设置正确工作的ItemsSource。

Public Function Convert(values() As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IMultiValueConverter.Convert 
    If values(0) IsNot Nothing AndAlso values(1) IsNot Nothing Then 
     Return DirectCast(values(0), ObservableCollection(Of CustomItem)).Where(Function(x) x.Code = CStr(values(1))).First().Source 
    End If 
    Return Binding.DoNothing 
End Function 

Public Function ConvertBack(value As Object, targetTypes() As Type, parameter As Object, culture As CultureInfo) As Object() Implements IMultiValueConverter.ConvertBack 
    Throw New NotImplementedException 
End Function

我试着对SelectedItem做类似的事情。在XAML：

<Border Tag="10"> 
<ComboBox DisplayMemberPath="Desc"> 
     <ComboBox.ItemsSource> 
      <MultiBinding Converter="{StaticResource comboSourceConverter}"> 
       <Binding Path="SourceList"/> 
       <Binding Path="Tag" RelativeSource="{RelativeSource AncestorLevel=1, Mode=FindAncestor, AncestorType=Border}" /> 
      </MultiBinding> 
     </ComboBox.ItemsSource> 
     <ComboBox.SelectedItem> 
      <MultiBinding Converter="{StaticResource comboSourceConverter}"> 
       <Binding Path="SourceList"/> 
       <Binding Path="Tag" RelativeSource="{RelativeSource AncestorLevel=1, Mode=FindAncestor, AncestorType=Border}" /> 
      </MultiBinding> 
     </ComboBox.SelectedItem> 
    </ComboBox>

转换器返回在组合框中选择了正确的值，但是这样一来就会提高对SOURCELIST属性设置方法，因为它是一个声明为第一路径在多重绑定中。

Public Function Convert(values() As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IMultiValueConverter.Convert 
    If values(0) IsNot Nothing AndAlso values(1) IsNot Nothing Then 
     Return DirectCast(values(0), ObservableCollection(Of CustomItem)).Where(Function(x) x.Code = CStr(values(1))).First().Selection 
End If 
    Return Binding.DoNothing 
End Function 

Public Function ConvertBack(value As Object, targetTypes() As Type, parameter As Object, culture As CultureInfo) As Object() Implements IMultiValueConverter.ConvertBack 
    Return New Object(){value} 
End Function

手动设置绑定一切正常，但我宁愿尽可能通过转换器做所有事情。

Dim _item As CustomItem = SourceList.Where(Function(x) x.Code = Border.Tag).FirstOrDefault() 
Dim _binding = New Binding("Selection") 
_binding.Mode = BindingMode.TwoWay 
_binding.Source = _item 
ComboBox.SetBinding(ComboBox.SelectedItemProperty, _binding)

来源

2017-06-07 Fabio L.

*“我试图做的的SelectedItem返回Selection属性类似” * - 请分享您所尝试的完整代码，以及它究竟如何失败。 “类似的东西”和“它不起作用”不足以让任何人猜测你做错了什么。 –

@EdPlunkett我的坏。我更新了我的问题。 –

您应该让XAML为您做更多的辛苦工作。让您的CustomItem一次，并绑定到其属性没有任何大惊小怪左右。

<Border DataContext="{Binding SourceList[10]}"> 
    <ComboBox 
     DisplayMemberPath="Desc" 
     ItemsSource="{Binding Source}" 
     SelectedItem="{Binding Selection}" 
     /> 
</Border>

这是什么意思。让我们呼吁SourceList[10]itemX：

var itemX = SourceList[10];

组合框将显示CustomValue在itemX.Source中发现的集合。
组合框将其选定的项目分配给itemX.Selection。

或者更好的是，这个。我不能肯定这是你在做什么的情况下，但它说明去想这个东西的方式：

<ItemsControl ItemsSource="{Binding SourceList}"> 
    <ItemsControl.ItemsTemplate> 
     <DataTemplate> 
      <!-- 
      Inside the DataTemplate, the DataContext will be one item 
      from SourceList. 
      --> 
      <Border> 
       <ComboBox 
        DisplayMemberPath="Desc" 
        ItemsSource="{Binding Source}" 
        SelectedItem="{Binding Selection}" 
        /> 
      </Border> 
     </DataTemplate> 
    </ItemsControl.ItemsTemplate> 
</ItemsControl>

来源

2017-06-07 18:52:26

第一个示例中使用的索引器不会在索引= 10的列表中获取项目吗？ –

@FabioL。我会更新以澄清。 –

@FabioL。查看更新。我猜对于您选择的项目想要做什么错了吗？ –

WPF组合框的SelectedItem动态绑定

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