Is there a way to specify a custom dependency property's default binding mode and update trigger?

Question

I would like to make it so that, as default, when I bind to one of my dependency properties the binding mode is two-way and update-trigger is property changed. Is there a way to do this?

Here is an example of one of my dependency properties:

public static readonly DependencyProperty BindableSelectionLengthProperty =
        DependencyProperty.Register(
        "BindableSelectionLength",
        typeof(int),
        typeof(ModdedTextBox),
        new PropertyMetadata(OnBindableSelectionLengthChanged));

Diego Mijelshon · Accepted Answer · 2010-04-18T23:15:58.407

115

When registering the property, initialize your metadata with:

new FrameworkPropertyMetadata
{
    BindsTwoWayByDefault = true,
    DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged
}

edited Apr 18 '10 at 23:15

answered Apr 18 '10 at 21:22

Diego Mijelshon

52,548
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3

I was able to set BindsTwoWayByDefault by adding this to my example dp: new FrameworkPropertyMetadata(0, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnBindableSelectionStartChanged). However, I am still having trouble setting the UpdateSourceTrigger to PropertyChanged. – Justin Apr 18 '10 at 21:47
1

I modified my answer to show how to do it with an object initializer. Use that instead of a constructor. – Diego Mijelshon Apr 18 '10 at 23:19
@DiegoMijelshon is there a way to allow only OneWay Binding mode ? – eran otzap Aug 19 '13 at 14:46
Very Cool,I'm just hunting for implementing TwoWay mode by hand. – zionpi Apr 18 '14 at 06:50
@Justin `DefaultUpdateSourceTrigger= UpdateSourceTrigger.PropertyChanged` does the trick – WiiMaxx Jan 30 '15 at 14:39
4

Guess it's worth noting that it's not possible to change the default to any other mode than `TwoWay`. So `OneTime` and `OneWayToSource` are excluded. At least I didn't find a way. – r41n Nov 17 '16 at 10:25

score 23 · Answer 2 · edited Mar 02 '16 at 08:45

In the Dependency Property declaration it would look like this:

public static readonly DependencyProperty IsExpandedProperty = 
        DependencyProperty.Register("IsExpanded", typeof(bool), typeof(Dock), 
        new FrameworkPropertyMetadata(true,
            FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
            OnIsExpandedChanged));

public bool IsExpanded
{
    get { return (bool)GetValue(IsExpandedProperty); }
    set { SetValue(IsExpandedProperty, value); }
}

Is there a way to specify a custom dependency property's default binding mode and update trigger?

2 Answers2

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