CODEWITHSUNDEEP
wpfbindingdependency-properties
andrea
andrea

Reputation: 1358

Cannot bind WPF DependencyProperty

I'm new to WPF and I'm try to bind a dependacy property. I want that the the text I write on the WPFCtrl:FilterTextBox will be displaied in the TextBlock

here is my XAML

    xmlns:WPFCtrl="clr-namespace:WPFControls"
    xmlns:local="clr-namespace:WpfApplication9"
    Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
    <local:Person x:Key="myDataSource" />
    </Window.Resources>
    <Grid>
    <StackPanel>
    <StackPanel.DataContext>
        <Binding Source="{StaticResource myDataSource}"/>
    </StackPanel.DataContext>
    <WPFCtrl:FilterTextBox Text="{Binding Path=Name, UpdateSourceTrigger=PropertyChanged }"/>
    <TextBlock Width="55" Height="25" Text="{Binding Path=Name, UpdateSourceTrigger=PropertyChanged}"/>
</StackPanel>
</Grid>

here the Person Class

namespace WpfApplication9
{
    public class Person : INotifyPropertyChanged
    {
        private string name = "";
        // Declare the event
        public event PropertyChangedEventHandler PropertyChanged;

        public Person()
        {
        }

        public Person(string value)
        {
            this.name = value;
        }

        public string Name
        {
            get { return name; }
            set
            {
                name = value;
                // Call OnPropertyChanged whenever the property is updated
                OnPropertyChanged("Name");
            }
        }

        // Create the OnPropertyChanged method to raise the event
        protected void OnPropertyChanged(string name)
        {
            PropertyChangedEventHandler handler = PropertyChanged;

            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(name));

            }
        }
    }   
}

and the FilterTextBox Text Property

 public static readonly DependencyProperty TextProperty = DependencyProperty.Register("Text", typeof(string), typeof(FilterTextBox), new PropertyMetadata());

    public string Text
    {
        //get { return _tbFilterTextBox.Text == null ? null : _tbFilterTextBox.Text.TrimEnd(); }
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
        //set { _tbFilterTextBox.Text = value; }
    }

The problem is that it does not enter in OnPropertyChanged() What am I doing wrong?

Upvotes: 0

Views: 1036

Answers (2)

Fredrik Hedblad
Fredrik Hedblad

Reputation: 84684

The problem is that the TextProperty in FilterTextBox doesn't bind TwoWay by default.

Either set the BindingMode to TwoWay

<WPFCtrl:FilterTextBox Text="{Binding Path=Name,
                                      Mode=TwoWay,
                                      UpdateSourceTrigger=PropertyChanged }"/>

Or change the metadata for the DependencyProperty Text so it binds twoway by default

public static readonly DependencyProperty TextProperty =
    DependencyProperty.Register("Text",
                                typeof(string),
                                typeof(FilterTextBox),
                                new FrameworkPropertyMetadata(null,
                     FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));

Upvotes: 1

Joachim Kerschbaumer
Joachim Kerschbaumer

Reputation: 9891

does this "FilterTextBox" Control update the DP everytime text is inserted?

i guess the FilterTextBox has a ControlTemplate with a regular TextBox inside. something like

<ControlTemplate TargetType="{x:Type FilterTextBox}">
 <TextBox Name="PART_FilterTextBoxInputField" Text="{TemplateBinding Text}"/>
</ControlTemplate>

you need to set the binding where the internal textbox binds to your Text-Dependcy Property to use UpdateSourceTrigger=PropertyChanged too. otherwise the binding will only update when the textbox loses focus.

Upvotes: 1

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