Question

Here is my situation. I have multiple user controls in a canvas. This canvas is saved out to a xaml file using XamlWriter. As most of you know, bindings are not saved using this method, so when I use XamlReader and read the user control back in, the binding no longer exists.

For a simple test, I have been trying to re-bind a ComboBox ItemsSource loaded from a XAML file (which is what I’m having issues with inside the User Control). I have tried implementing INotifyPropertyChanged, however, my variable:

public event PropertyChangedEventHandler PropertyChanged

is always null when I try and set the ComboItemsProperty:

public ObservableCollection<string> ComboItemsProperty
{
    get { return ComboItems; } //Field
    set 
    {
        ComboItems = value;
        OnPropertyChanged("ComboItemsProperty");
    }

So, my ultimate goal is to load a xaml file and then add items to a ComboBox’s ItemsSource and then have the ComboBox update with the new items.

Am I going about this the wrong way? Could someone provide me with a simple working example of this?

EDIT:

protected void OnPropertyChanged(string propertyName)
{
    PropertyChangedEventHandler handler = PropertyChanged
    if (PropertyChanged != null)
    {
         handler(this, new PropertyChangedEventArgs(propertyName));
    }
}

I’m fairly certain it has something to do with loading the XAML and the binding no longer being set. I have tried setting the binding, but no luck.

2nd EDIT:

I think I’m 99% sure that the binding is the cause. My OnPropertyChanged works fine as long as I didn’t load the combobox from a file. I have tried setting the binding as follows:

Binding bind = new Binding();
bind.Mode = BindingMode.TwoWay;
bind.Source = this.ComboItemsProperty; //Not sure about this line.
bind.Path = new PropertyPath("ComboItemsProperty");
this.SetBiding(ComboBox.ItemsSourceProperty, bind);

Confirmed. When I bring back in a simple combobox, my attempt to bind it is not working. It must be something in the code above.

Answer 1

bind.Source needs to point to the object containing ComboItemsProperty, not the property itself.

Binding bind = new Binding();
bind.Mode = BindingMode.TwoWay;
bind.Source = this;
bind.Path = new PropertyPath("ComboItemsProperty");
this.SetBiding(ComboBox.ItemsSourceProperty, bind);

You can check the binding succeeded with:

 if (GetBindingExpression(ComboBox.ItemsSourceProperty).Status != BindingStatus.Active)
 { 
    //binding didn't work
 }