MultiDataTrigger with OR instead of AND

Question

I am trying to set multiple DataTriggers on my Button. I did some research and found that MultiDataTrigger allows you to do this. I want the Visibility property of my Button to be set to false if the CCTVPath == string.Empty OR PermissionsFlag == false. This is what I have so far;

<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>

And in my code-behind I set PermissionsFlag like so;

public bool PermissionsFlag { get; set; }

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

As you can see PermissionsFlag is definitely false, and the there are definitely empty CCTVPath however the Button is never hidden. What am I doing wrong?

UPDATE:

    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;
    }

In my XAML:

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

Answer 1

tranform Conditions into two independent 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>

make sure that binding paths are correct (check VS Output window for possible exception messages)

---

also: don't rely only on hidden state of Button, implement permissions properly in code (OnCCTVButtonClick). read why here:

How to Snoop proof your wpf application?

---

---

auto-property PermissionsFlag (public bool PermissionsFlag { get; set; }) doesn't notify view about changes.

it is possible to implement INotifyPropertyChanged interface (in my test window it is done like this: public partial class Window3 : Window, INotifyPropertyChanged) and then raise event when property changes.

here is a complete working example which I used for test

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));
    }
}

window 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>