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How to bind a Control.Property to a property in the code-behind?

Answer 1

+1 A:

You have to set the DataContext of the TextBox control (or of any of its parents) to your window:

myTextBox.DataContext = this;

then in your XAML:

<TextBox Text={Binding Text} x:Name="myTextBox"/>

Mart 2009-11-14 17:49:09

Does that property has to be a DependencyProperty?

Shimmy 2009-11-14 17:57:54

Depending on the declaration of your Text property (which should be a DependencyProperty), you may have to explicitly set a TwoWay binding: {Binding Text, Mode=TwoWay}

Mart 2009-11-14 18:00:18

It can be a DependencyProperty (use the propdp code snippet in Visual Studio) or the object can implement the INotifyPropertyChanged interface.

Mart 2009-11-14 18:03:47

I actually don't need it as a two way, i only want that when the Window.Text is changed the TextBox.Text should be updated.

Shimmy 2009-11-14 18:06:41

@Mart, can you be more specific, I think I like what you say

Shimmy 2009-11-14 18:10:06

If you define your Window.Text as a DependencyProperty, the TextBox.Text will be updated automatically. Example of a DP definition:public string Text{ get { return (string)GetValue(TextProperty); } set { SetValue(TextProperty, value); }}public static readonly DependencyProperty TextProperty = DependencyProperty.Register("Text", typeof(string), typeof(Window), new UIPropertyMetadata(string.Empty));

Mart 2009-11-14 18:13:50

Thanks for your effort and sorry for not telling you my exact question. I meant how could I do this using the INotifyPropertyChanged tha you said above.

Shimmy 2009-11-14 18:29:36

The INotifyPropertyChanged interface is used when you want to bind a whole object rather than a single dependency property. Basically each of your object's property raises a PropertyChanged event in its setter. This way WPF knows the value has changed and reflects it to the user interface.

Mart 2009-11-14 18:43:58

I think this is what I am looking for, what message do I have to call at the property (a regular property, right?)?

Shimmy 2009-11-14 21:13:06

Each time a (regular) property value is changed, a PropertyChanged event is raised. Example:public event PropertyChangedEventHandler PropertyChanged;protected void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); }private string _text;public string Text { get { return _text; } set { if (_text != value) { _text = value; OnPropertyChanged("Text"); } } }

Mart 2009-11-14 23:52:09

But I am using it in a window where the OnPropertyChanged method is already implemented asking me to pass DependencyPropertryChangedEventArgs as a param?

Shimmy 2009-11-15 00:05:16

As I told you, if your property is attached to the window, you should have a DependencyProperty as described before. The INotifyPropertyChanged technique is used when you bind to a custom class.

Mart 2009-11-15 00:17:24

Thanks for all your help!

Shimmy 2009-11-15 00:18:32

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How to bind a Control.Property to a property in the code-behind?

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