c# – 使用OR而不是AND的MultiDataTrigger

发布时间：2020-12-15 08:11:47 所属栏目：百科来源：网络整理

导读：我想在我的Button上设置多个DataTriggers.我做了一些研究,发现MultiDataTrigger允许你这样做.如果CCTVPath == string.Empty OR PermissionsFlag == false,我希望我的Button的Visibility属性设置为false.这就是我到目前为止所拥有的; Button Grid.Column="3"

我想在我的Button上设置多个DataTriggers.我做了一些研究,发现MultiDataTrigger允许你这样做.如果CCTVPath == string.Empty OR PermissionsFlag == false,我希望我的Button的Visibility属性设置为false.这就是我到目前为止所拥有的;

<Button Grid.Column="3" x:Name="cctvFeedButton" Content="Live Feed"
        Width="100" FontSize="16" HorizontalAlignment="Right" Margin="5" Click="OnCCTVButtonClick">
    <Button.Style>
        <Style TargetType="Button">
            <Style.Triggers>
                <MultiDataTrigger>
                    <MultiDataTrigger.Conditions>
                        <Condition Binding="{Binding CCTVPath}" Value=""/>
                        <Condition Binding="{Binding PermissionsFlag}" Value="False"/>
                    </MultiDataTrigger.Conditions>
                    <Setter Property="Visibility" Value="Hidden"/>
                </MultiDataTrigger>
            </Style.Triggers>
        </Style>
    </Button.Style>
</Button>

在我的代码隐藏中,我设置PermissionsFlag就像这样;

public bool PermissionsFlag { get; set; }

private void OnPageLoaded(object sender,RoutedEventArgs e)
{
    PermissionsFlag = false;
}

正如你所看到的PermissionsFlag肯定是假的,并且肯定是空CCTVPath但是Button永远不会被隐藏.我究竟做错了什么？

更新：

public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this,new PropertyChangedEventArgs(propertyName));
    }

    private bool _permissionsFlag;
    public bool Flag
    {
        get { return _permissionsFlag; }
        set
        {
            _permissionsFlag = value;
            OnPropertyChanged("PermissionsFlag");
        }
    }

    private void OnPageLoaded(object sender,RoutedEventArgs e)
    {
        Flag = false;
        CCTVImageCollection = GetImages();
        imageListBox.ItemsSource = CCTVImageCollection;
        DataContext = this;
    }

在我的XAML中：

<Button.Style>
         <Style TargetType="Button">
               <Style.Triggers>
                      <DataTrigger Binding="{Binding PermissionsFlag}" Value="False">
                            <Setter Property="Visibility" Value="Hidden"/>
                      </DataTrigger>
               </Style.Triggers>
         </Style>
 </Button.Style>

解决方法

将条件转换为两个独立的DataTriggers

<Style.Triggers>
    <DataTrigger Binding="{Binding CCTVPath}" Value="">
        <Setter Property="Visibility" Value="Hidden"/>
    </DataTrigger>
    <DataTrigger Binding="{Binding PermissionsFlag}" Value="False">
        <Setter Property="Visibility" Value="Hidden"/>
    </DataTrigger>
</Style.Triggers>

确保绑定路径正确(检查VS Output窗口是否有可能的异常消息)

另外：不要只依赖Button的隐藏状态,在代码中正确实现权限(OnCCTVButtonClick).在这里阅读原因：

How to Snoop proof your wpf application?

auto-property PermissionsFlag(public bool PermissionsFlag {get; set;})不会通知视图有关更改.

可以实现INotifyPropertyChanged接口(在我的测试窗口中它是这样完成的：公共部分类Window3：Window,INotifyPropertyChanged)然后在属性更改时引发事件.

这是一个完整的工作示例,我用于测试

public partial class Window3 : Window,INotifyPropertyChanged
{
    public Window3()
    {
        InitializeComponent();
        this.DataContext = this;
        //PermissionsFlag = true;
        CCTVPath = "youtube.com";
    }

    private bool _permissionsFlag = false;
    private string _cctvPath;

    public bool PermissionsFlag
    {
        get { return _permissionsFlag; }
        set
        {
            _permissionsFlag = value;
            OnPropertyChanged("PermissionsFlag");
        }
    }

    public string CCTVPath
    {
        get { return _cctvPath; }
        set
        {
            _cctvPath = value;
            OnPropertyChanged("CCTVPath");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this,new PropertyChangedEventArgs(propertyName));
    }
}

窗口xaml：

<Window x:Class="WpfDemos.Views.Window3"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window3" Height="300" Width="300">
    <StackPanel>
        <CheckBox Name="chkPermissionsFlag" 
                  Content="PermissionsFlag" 
                  IsChecked="{Binding Path=PermissionsFlag,UpdateSourceTrigger=PropertyChanged}"/>

        <TextBox Text="{Binding Path=CCTVPath,UpdateSourceTrigger=PropertyChanged}"/>

        <Button x:Name="cctvFeedButton" Content="Live Feed"
                    Width="100" FontSize="16" HorizontalAlignment="Right" Margin="5">
            <Button.Style>
                <Style TargetType="Button">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding Path=CCTVPath}" Value="">
                            <Setter Property="Visibility" Value="Hidden"/>
                        </DataTrigger>
                        <DataTrigger Binding="{Binding Path=PermissionsFlag}" Value="False">
                            <Setter Property="Visibility" Value="Hidden"/>
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </Button.Style>
        </Button>
    </StackPanel>
</Window>

（编辑：李大同）

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