CODEWITHSUNDEEP
c#wpfxamltriggers
Edward Tanguay
Edward Tanguay

Reputation: 193282

How can I change the Visibility of a TextBlock with a Trigger?

When I try to compile the following code, I get the error 'Visibility' member is not valid because it does not have a qualifying type name.

What do I have to change so that I can make the TextBlock disappear when Status=off?

XAML:

<Window x:Class="TestTrigger123345.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <StackPanel>
        <TextBlock Text="This is a sentence.">
            <TextBlock.Triggers>
                <Trigger Property="{Binding Status}" Value="off">
                    <Setter Property="Visibility" Value="Collapsed"/>
                </Trigger>
            </TextBlock.Triggers>
        </TextBlock>
        <TextBlock Text="{Binding Status}"/>
    </StackPanel>
</Window>

Code Behind:

using System.Windows;

namespace TestTrigger123345
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            DataContext = this;
            Status = "off";
        }

        public string Status { get; set; }

    }
}

I changed to DataTrigger and Dependency Properties and it gets the same error:

XAML:

<Window x:Class="TestTrigger123345.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <StackPanel HorizontalAlignment="Left">
        <TextBlock Text="{Binding Status}">
            <TextBlock.Triggers>
                <DataTrigger Binding="{Binding Status}" Value="off">
                    <Setter Property="TextBlock.Background" Value="Tan"/>
                </DataTrigger>
            </TextBlock.Triggers>
        </TextBlock>
    </StackPanel>
</Window>

Code Behind:

using System.Windows;

namespace TestTrigger123345
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            DataContext = this;
            Status = "off";
        }

        #region DependencyProperty: Status
        public string Status
        {
            get
            {
                return (string)GetValue(StatusProperty);
            }
            set
            {
                SetValue(StatusProperty, value);
            }
        }

        public static readonly DependencyProperty StatusProperty =
            DependencyProperty.Register("Status", typeof(string), typeof(Window1),
            new FrameworkPropertyMetadata());
        #endregion


    }
}

I redid this with a ViewModel that has a property Status that implements INotifyPropertyChanged, and it gets that same error:

WindowViewModel.cs:

using System.ComponentModel;

namespace TestTrigger123345
{
    class WindowViewModel
    {
        #region ViewModelProperty: Status
        private string _status;
        public string Status
        {
            get
            {
                return _status;
            }

            set
            {
                _status = value;
                OnPropertyChanged("Status");
            }
        }
        #endregion

        #region PropertChanged Block
        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(string property)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(property));
            }
        }
        #endregion
    }
}

Code Behind:

using System.Windows;

namespace TestTrigger123345
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            WindowViewModel windowViewModel = new WindowViewModel();
            windowViewModel.Status = "off";
            DataContext = windowViewModel;
        }

    }
}

Surely there is a way to do this with a trigger somehow.

Upvotes: 22

Views: 28244

Answers (5)

Yuri Perekupko
Yuri Perekupko

Reputation: 93

Try something like this:

<PasswordBox Name="pbxPassword" />
<TextBox Text="{Binding Password,
                        ElementName=pbxPassword,
                        UpdateSourceTrigger=PropertyChanged}">
    <TextBox.Style>
        <Style TargetType="TextBox">
            <Setter Property="Visibility" Value="Hidden" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding IsChecked, ElementName=chbShowPassword}" Value="True">
                    <Setter Property="Visibility" Value="Visible" />
                </DataTrigger>                  
            </Style.Triggers>
        </Style>
    </TextBox.Style>
</TextBox>
<CheckBox Name="chbShowPassword">
    Show password
</CheckBox>

Upvotes: 6

Tecky
Tecky

Reputation: 56

Triggers of an element only support EventTrigger so you can't use property triggers (Trigger). Look FrameworkElement.Triggers Property.

Upvotes: 2

Will Perry
Will Perry

Reputation: 601

You need to specify the Type on which the visibility should be set

<Setter Property="FrameworkElement.Visibility" Value="Visible"/>

Upvotes: 60

Arcturus
Arcturus

Reputation: 27055

For Bindings use DataTrigger, for properties you can use Trigger.. Also make sure the Status Property notifies ;) Either make it a dependency property or use the INotifyPropertyChanged interface.

DataTrigger on MSDN

Nice article how to combine all these trigger goodness

Upvotes: 0

rockeye
rockeye

Reputation: 2773

Maybe you need to implement INotifyPropertyChanged and raise PropertyChange when Status change ?

Instead of using a trigger, you can use a Converter between Visibility and your Status string.

Upvotes: 0

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