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WPF/VB.net新手在这里。WPF中的过滤项目在VB.net datagrid
我想筛选数据网格中的行并玩得开心。
我已经成功创建了一个对象列表，并使用itemsource属性来获取要填充的数据网格。
现在我有一个复选框，为了参数 - 我只想点击并过滤只符合这个标准的那些行。
通过下面的代码，我得到了一般性的“对象引用未设置为对象的实例”。错误，但有点丢失。我相信一个VB专业人士会看到它。
我宁愿在代码中做更多，而不是尽可能使用XAML。
这是我的XAML：
<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>
<DataGrid x:Name="displayGrid" HorizontalAlignment="Left" Margin="62,94,0,0" VerticalAlignment="Top" Height="142" Width="360" SelectionChanged="DataGrid_SelectionChanged"/>
<Button Content="Load" HorizontalAlignment="Left" Margin="62,51,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>
<CheckBox x:Name="showOnlyChildren" Content="Show Only Children" HorizontalAlignment="Left" Margin="172,51,0,0" VerticalAlignment="Top" Width="147"/>
</Grid>
</Window>
这是我的代码：
Class MainWindow
Class person
Property name
Property age
End Class
Dim listOfPersons As New List(Of person)
Private filteredList As CollectionViewSource
Private Sub DataGrid_SelectionChanged(sender As Object, e As SelectionChangedEventArgs)
End Sub
Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
Dim aPerson As New person With {
.name = "Fred Smith",
.age = 12}
listOfPersons.Add(aPerson)
Dim bPerson As New person With {
.name = "Tom Jones",
.age = 50}
listOfPersons.Add(bPerson)
displayGrid.ItemsSource = CollectionViewSource.GetDefaultView(listOfPersons)
End Sub
Private Sub ShowOnlyChildrenFilter(ByVal sender As Object, ByVal e As FilterEventArgs)
Dim person As person = TryCast(e.Item, person)
If person IsNot Nothing Then
' Filter out persons with age less than 18
If person.age < 19 Then
e.Accepted = True
Else
e.Accepted = False
End If
End If
End Sub
Private Sub AddFiltering(ByVal sender As Object, ByVal args As RoutedEventArgs) Handles showOnlyChildren.Checked
AddHandler filteredList.Filter, AddressOf ShowOnlyChildrenFilter
End Sub
Private Sub RemoveFiltering(ByVal sender As Object, ByVal args As RoutedEventArgs)
RemoveHandler filteredList.Filter, AddressOf ShowOnlyChildrenFilter
End Sub
End Class
编辑：OK缓慢而稳步地到达那里。我加入了一些变化，我发现here和感谢帮助我来到这里....这是代码看起来像现在：
Imports System.ComponentModel
Class MainWindow
Class person
Property name
Property age
End Class
Dim listOfPersons As New List(Of person)
Private filteredList As CollectionViewSource
Dim view As ICollectionView
Private Sub DataGrid_SelectionChanged(sender As Object, e As SelectionChangedEventArgs)
End Sub
Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
Dim aPerson As New person With {
.name = "Fred Smith",
.age = 12}
listOfPersons.Add(aPerson)
Dim bPerson As New person With {
.name = "Tom Jones",
.age = 50}
listOfPersons.Add(bPerson)
view = CollectionViewSource.GetDefaultView(listOfPersons)
displayGrid.ItemsSource = view
End Sub
Function ShowOnlyChildrenFilter(ByVal param As Object) As Boolean
Dim person As person = TryCast(param, person)
Dim retValue As Boolean
If person IsNot Nothing Then
' Filter out persons with age less than 18
If person.age < 19 Then
retValue = True
Else
retValue = False
End If
End If
Return retValue
End Function
Private Sub showOnlyChildren_Checked(sender As Object, e As RoutedEventArgs) Handles showOnlyChildren.Checked
If showOnlyChildren.IsChecked = True Then
view.Filter = New Predicate(Of Object)(AddressOf ShowOnlyChildrenFilter)
Else
'what goes here?
End If
End Sub
End Class
我唯一缺少的是如何刷新数据网格，当复选框未选中时。谢谢大家。我仍然很惊讶这是多么复杂和大胆的想法，因为我认为这很简单。
什么线给你的错误？ – Steve
@Steve AddHandler filteredList.Filter，AddressOf ShowOnlyChildrenFilter，当我点击复选框。我在CollectionViewSource前添加了New关键字，现在不会出现错误。只是不做我想要的。 – bendecko
我没有看到你在发布的代码中引用的行？ – Steve