How to force a WPF binding to refresh?

Question

I have got a combo box with items source attached using simple binding. Is there any way to refresh this binding once combo box is loaded?

Cyrenaica

What do you mean by simple binding? Normally when you use binding the control should automatically refresh. – Barneybarnhart

Techee, no offence, but I believe H.B. deserves his answer to be accepted ;-) – Pitchford

@Pitchford I'm not sure Techee is ever coming back - six and a half years since he's been logged in – Plast

I don't really understand what is being asked. Is the entire collection being changed? Only its contents? What type of collection is being used? There is not enough detail. – Haematinic

Answer 1

You can use binding expressions:

private void ComboBox_Loaded(object sender, RoutedEventArgs e)
{
    ((ComboBox)sender).GetBindingExpression(ComboBox.ItemsSourceProperty)
                      .UpdateTarget();
}

But as Blindmeis noted you can also fire change notifications, further if your collection implements INotifyCollectionChanged (for example implemented in the ObservableCollection<T>) it will synchronize so you do not need to do any of this.

Saxton

Doesn't seem to do a thing for me using a ListBox. – Thun

@JonathanWood: Well, i cannot divine what kind of code you have, including what your binding looks like. Does the binding even work in the first place? – Saxton

Answer 2

if you use mvvm and your itemssource is located in your vm. just call INotifyPropertyChanged for your collection property when you want to refresh.

OnPropertyChanged(nameof(YourCollectionProperty));

Quiteri

This is the cleanest approach imho. – Tripetalous

This should be done where possible, but it should be noted it's not always practical. For instance if you're binding to a serial port, and want to check whether it's open, closed, the baud rate, etc you can create a wrapper class around the serial port that implements INotifyPropertyChanged, but you will have to keep the port private to that wrapper and thus need to write a property and method for everything on that port you use elsewhere in the project to ensure that the properties you are interested in notifying on always go through the wrapper – Emmert

Point to Note : This will not update the UI when there is an item added or removed from list. For this scenario you have to use observable collection – Denbrook

if you call OnPropertyChanged(nameof(YourCollectionProperty)); after adding or removing an item - it works. but you are right observable collection to this build in. – Quiteri

Answer 3

To add my 2 cents, if you want to update your data source with the new value of your Control, you need to call UpdateSource() instead of UpdateTarget():

((TextBox)sender).GetBindingExpression(TextBox.TextProperty).UpdateSource();

Deport

Answer 4

MultiBinding friendly version...

private void ComboBox_Loaded(object sender, RoutedEventArgs e)
{
    BindingOperations.GetBindingExpressionBase((ComboBox)sender, ComboBox.ItemsSourceProperty).UpdateTarget();
}

Annulate

Answer 5

Try using BindingExpression.UpdateTarget()

Euthenics