Custom UserControl “IsEnabled” data binding not working

Question

I have a kinda awful problem with my WPF application right now...

I have a custom UserControl used to edit details of a component. It should start by being not enabled, and become enabled as soon as the user chose a component to edit.

The problem is: the IsEnabled property does not even change.

Here is my code:

<my:UcComponentEditor Grid.Column="1" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"  
                        IsEnabled="{Binding EditorEnabled}"
                              DataContext="{Binding VmComponent}" />

EditorEnabled is a property in my ViewModel (VmComponent), and is by default false, becomes true when the user chose a component or created one

Just for the record, in my ViewModel:

private Boolean _editorEnabled = false;

    public Boolean EditorEnabled
    {
        get { return _editorEnabled; }
        set 
        {
            _editorEnabled = value;
            OnPropertyChanged("EditorEnabled");
        }
    }

When I try to launch my app, the UserControl is starting... enabled. I added breakpoints everywhere, the EditorEnabled is false from the beginning.

I also did a horribly stupid thing to try to figure out what's happening: I created a converter (so useful -- converting a boolean to boolean -- eh), put a breakpoint on it, and... The code is never reached.

<my:UcComponentEditor Grid.Column="1" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"  
                        IsEnabled="{Binding EditorEnabled, Converter={StaticResource BoolConverter}}"
                              DataContext="{Binding VmComponent}" />

That probably means that the property isEnabled is never set, since the converter is never reached.

Do you see any kind of problem there? I started working in WPF about one week ago and therefore I may have missed something essential...

Thank you very much for your time :-)

Answer 1

You should add a DependencyProperty for the binding to work properly. See here for more information.

Code-behind:

public static readonly DependencyProperty EditorEnabledDependencyProperty = DependencyProperty.Register("EditorEnabled", typeof(bool), typeof(UcComponentEditor), new PropertyMetadata(false));

public bool EditorEnabled
{
    get { return (bool)base.GetValue(UcComponentEditor.EditorEnabledDependencyProperty); }
    set { base.SetValue(UcComponentEditor.EditorEnabledDependencyProperty, value); }
}

Answer 2

The issue I think is that there is a binding on the DataContext property of the user control. Which means the EditorEnabled property should be a property in the VmComponent object. At least that's what my problem was.

To get around it, I specified a proper source to the binding of IsEnabled. Once I did that the control started working as expected.

Hope that helps.

Answer 3

Encapsulating your control in a DockPanel (for example) will remove the need for a DependencyProperty.

You can then simply do your binding with the dockpanel instead of the custom control. Setting the variable bound to IsEnabled on the Dockpanel will automatically enable or disable the items contained in the Dockpanel.