Question

我有两个菜单项元素 - “Undelete”和“Delete”具有互补可见性：当显示一个时，另一个被隐藏。

在ViewModel的代码中，我有一个依赖属性FilesSelectedCanBeUndeleted定义如下：

private bool _filesSelectedCanBeUndeleted;
public bool FilesSelectedCanBeUndeleted
{
    get
    {
        return _filesSelectedCanBeUndeleted;
    }
    set
    {
        _filesSelectedCanBeUndeleted = value;
        OnPropertyChanged("FilesSelectedCanBeUndeleted");
    }
}

Undelete按钮的XAML如下所示：

<MenuItem Header="Undelete" Command="{Binding UndeleteCommand }" 
Visibility="{Binding Path=FilesSelectedCanBeUndeleted, 
Converter={StaticResource BoolToVisConverter}}" >

正如您所见，Undelete的Visibility绑定到FilesSelectedCanBeUndeleted property（在BooleanToVisibilityConveter的帮助下）。

现在我的问题是，如何编写XAML以将Delete按钮的Visibility绑定到FilesSelectedCanBeUndeleted属性的“NOT”值？

谢谢，

Answer 1

Here是自定义IValueConverter的示例，它允许您反转可见性逻辑。基本上，当view-model属性为true时，一个MenuItem将可见，而另一个将被折叠。

所以你需要像这样定义转换器的两个实例：

<local:BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
<local:BooleanToVisibilityConverter x:Key="ReversedBooleanToVisibilityConverter" IsReversed="true" />

Answer 2

你可以使用将datatrigger应用到menuitem以避免你的viemodel中的另一个属性 -

        <MenuItem Header="Delete"
                  Command="{Binding DeleteCommand }">
            <MenuItem.Style>
                <Style TargetType="{x:Type MenuItem}">
                    <Setter Property="Visibility" Value="Visible" />
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding FilesSelectedCanBeUndeleted}" Value="False">
                            <Setter Property="Visibility"
                                    Value="Collapsed" />
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </MenuItem.Style>
        </MenuItem>

Answer 3

在ViewModel上创建新属性，然后取消'FilesSelectedCanBeUndeleted'，然后绑定到它。

Answer 4

我刚才做了类似的事情，只是简单地否定了......

    private bool _filesSelectedCanBeUndeleted;
public bool FilesSelectedCanBeUndeleted{    
        get{ 
            return _filesSelectedCanBeUndeleted;    
            }   
        set{        
            _filesSelectedCanBeUndeleted = value;        
            OnPropertyChanged("FilesSelectedCanBeUndeleted");    
            // You have also to notify that the second Prop will change
            OnPropertyChanged("FilesSelectedCanBeDeleted");    
            }}

public bool FilesSelectedCanBeDeleted{
        get{
            return !FilesSelectedCanBeUndeleted;
        }
        }

Xaml看起来就像这样......

<MenuItem Header="Delete" 
    Command="{Binding DeleteCommand }" 
    Visibility="{Binding Path=FilesSelectedCanBeDeleted, Converter={StaticResource BoolToVisConverter}}" >

将两个元素的可见性绑定到一个属性

4 个答案: