Wpf-无法将MenuItem转换为Listbox？ [英] Wpf- Unable to cast MenuItem to Listbox?

问题描述

我遇到了一个非常奇怪的例外。
我得到例外：

'set connectionId抛出一个异常'行号'26'和行位置'34' 。

当我看到内部异常我得到：

无法转换类型为System.Windows.Controls.MenuItem的对象键入System.Windows.Controls.ListBox。

我将此例中的原因缩小到此 TreeView MenuItem >：

 < TreeView x：Name =ProjectElementTreeViewItemsSource ={Binding ProjectElementCollection}DisplayMemberPath =Name =0SelectedItemChanged =ProjectElementTreeView_SelectedItemChangedGotKeyboardFocus =ProjectElementTreeView_GotKeyboardFocus> 
< TreeView.Resources> 
< Style TargetType ={x：Type TreeViewItem}> 
< Setter Property =Horizo​​ntalAlignmentValue =Left/> 
< Setter Property =ContextMenu> 
< Setter.Value> 
< ContextMenu> 
< MenuItem Name =AddProjectElementMenuItemHeader =AddClick =AddProjectElementMenuItem_Click/> 
< / ContextMenu> 
< /Setter.Value> 
< / Setter> 
< / Style> 
< /TreeView.Resources> 
< / TreeView> 
  

仅在 MenuItem 有一个点击事件处理程序，即使点击事件处理程序不包含任何代码也会抛出。

解决方案

我有同样的例外你做了看到更接近代码之后，这感觉就像一个你会得到

不能指定事件'点击'
在Style中的Target标签上，使用
EventSetter。

我不知道为什么

无论如何，使用EventSetter可以使用

  < Setter.Value> 
< ContextMenu> 
< MenuItem Name =AddProjectElementMenuItemHeader =Add> 
< MenuItem.Style> 
< Style TargetType =MenuItem> 
< EventSetter Event =点击Handler =AddProjectElementMenuItem_Click/> 
< / Style> 
< /MenuItem.Style> 
< / MenuItem> 
< / ContextMenu> 
< /Setter.Value> 
< / Setter> 
  

I am getting a very strange exception. I get the exception:

"'Set connectionId threw an exception.' Line number '26' and line position '34'."

When I look at the Inner Exception I get:

"Unable to cast object of type 'System.Windows.Controls.MenuItem' to type 'System.Windows.Controls.ListBox'."

I have narrowed the cause of the exception to the MenuItem in the TreeViewItem style contained in this TreeView:

<TreeView x:Name="ProjectElementTreeView" ItemsSource="{Binding ProjectElementCollection}"  DisplayMemberPath="Name" Padding="0" SelectedItemChanged="ProjectElementTreeView_SelectedItemChanged" GotKeyboardFocus="ProjectElementTreeView_GotKeyboardFocus">
        <TreeView.Resources>
            <Style TargetType="{x:Type TreeViewItem}">
                <Setter Property="HorizontalAlignment" Value="Left" />
                <Setter Property="ContextMenu">
                    <Setter.Value>
                        <ContextMenu>
                            <MenuItem Name="AddProjectElementMenuItem" Header="Add" Click="AddProjectElementMenuItem_Click"/>
                        </ContextMenu>
                    </Setter.Value>
                </Setter>
            </Style>
        </TreeView.Resources>
    </TreeView>

The exception only occurs when the MenuItem has a click event handler and is thrown even when the click event handler does not contain any code.

解决方案

I got the same exception as you did. After looking closer at the code, this feels like a situation where you would get

"The event 'Click' cannot be specified on a Target tag in a Style. Use an EventSetter instead."

I'm not sure why that doesn't apply here.
Anyway, using an EventSetter works

<Setter Property="ContextMenu">
    <Setter.Value>
        <ContextMenu>
            <MenuItem Name="AddProjectElementMenuItem" Header="Add">
                <MenuItem.Style>
                    <Style TargetType="MenuItem">
                        <EventSetter Event="Click" Handler="AddProjectElementMenuItem_Click"/>
                    </Style>
                </MenuItem.Style>
            </MenuItem>
        </ContextMenu>
    </Setter.Value>
</Setter>

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