问题描述
我尽量让定制的ListView如果具体的继承类希望如此,填补了一些东西,最初的复选框每个列表项。当前未显示复选框,所以我想的东西ContentControl中我的code是莫名其妙的错误。
I try to make a customized ListView which fills each list item with some stuff and an initial Checkbox if the concrete inheriting class wishes so. Currently no Checkbox is displayed so I guess my code of the ContentControl stuff is somehow erroneous.
<UserControl x:Class="local:MyListView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="some/path/here">
<ListView>
<ListView.View>
<GridView>
<GridViewColumn>
<GridViewColumn.CellTemplate>
<DataTemplate>
<!-- Each list item: [Checkbox] Label -->
<StackPanel Orientation="Horizontal">
<!-- The code for the optional check box -->
<ContentControl>
<ContentControl.Style>
<Style TargetType="ContentControl">
<Style.Triggers>
<DataTrigger Binding="{Binding IsCheckable, RelativeSource={RelativeSource AncestorType=local:MyListView}}"
Value="True">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<CheckBox IsChecked="{Binding Path=SomeProperty}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
<!-- The non-optional test label -->
<Label Content="Test Content" />
</StackPanel>
</DataTemplate>
</GridViewColumn.CellTemplate>
</GridViewColumn>
</ListView.View>
</ListView>
</UserControl>
在code背后:
The Code behind:
abstract partial class MyListView {
protected MyListView () {
InitializeComponent();
}
protected abstract bool IsCheckable { get; }
}
// A checkbox should be displayed - but it's not...
public class MyListView1 : MyListView {
protected bool IsCheckable { get { return true; } }
}
public class MyListView2 : MyListView {
protected bool IsCheckable { get { return false; } }
}
在检查输出窗口,我发现以下消息(我不知道如何利用):
When inspecting the output window I discovered following message (that I don't know how to make use of):
System.Windows.Data信息:10:使用绑定和没有有效的回退值存在无法检索值;使用默认值来代替。 BindingEx pression:路径= IsCheckable;的DataItem ='MyListView2'(名称='');目标元素是'ContentControl中'(名称=''); target属性是'NoTarget'(类型'对象')
System.Windows.Data错误:39:BindingEx pression路径错误:'IsCheckable'属性不是'对象'''MyListView2'(名称='')'找到。 BindingEx pression:路径= IsCheckable;的DataItem ='MyListView2'(名称='');目标元素是'ContentControl中'(名称=''); target属性是'NoTarget'(类型'对象')
System.Windows.Data Error: 39 : BindingExpression path error: 'IsCheckable' property not found on 'object' ''MyListView2' (Name='')'. BindingExpression:Path=IsCheckable; DataItem='MyListView2' (Name=''); target element is 'ContentControl' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data信息:19:BindingEx pression不能因为缺少信息检索值。 BindingEx pression:路径= IsCheckable;的DataItem ='MyListView2'(名称='');目标元素是'ContentControl中'(名称=''); target属性是'NoTarget'(类型'对象')
System.Windows.Data Information: 19 : BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=IsCheckable; DataItem='MyListView2' (Name=''); target element is 'ContentControl' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data信息:20:BindingEx pression无法检索空数据项值。被分离或绑定到没有任何价值可空类型时,结合时,这可能发生。 BindingEx pression:路径= IsCheckable;的DataItem ='MyListView2'(名称='');目标元素是'ContentControl中'(名称=''); target属性是'NoTarget'(类型'对象')
System.Windows.Data Information: 20 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=IsCheckable; DataItem='MyListView2' (Name=''); target element is 'ContentControl' (Name=''); target property is 'NoTarget' (type 'Object')
同样的错误信息出现MyListView1。
请注意,这个问题从<一个进化产生href=\"http://stackoverflow.com/questions/12202294/how-to-conditionally-insert-a-checkbox-in-a-list-item-of-a-customized-listview?answertab=active#tab-top\">an旧的帖子。
The same error messages appear for MyListView1.Note that this question arose from the evolution of an older post.
推荐答案
据该的
属性使用作为约束源属性的绑定必须
是你的类的公共属性。明确定义的接口
属性不能结合的目的被访问,也不能保护
具有没有碱专用内部或虚拟属性
实施
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