Question

In a window I have a textbox and I’m using a canExecute function to check if the field is empty or not. I have a to-way binding on the DependencyProperty used inside the textbox. Anyway it is always null in CanExecute (Edit : it’s not null, it’s empty : “”). Can you tell me where is the mistake ?

<TextBox Text="{Binding Path=StatusName, ElementName=Window, Mode=TwoWay}" x:Name="StatusNameTextBox" />

---

public String StatusName
    {
        get { return (String)GetValue(StatusNameProperty); }
        set { SetValue(StatusNameProperty, value); }
    }

public static readonly DependencyProperty StatusNameProperty =
        DependencyProperty.Register("StatusName", typeof(String), typeof(AddStatusWindow), new UIPropertyMetadata(""));

private void AddNewStatusCommand_CanExecute(object sender, CanExecuteRoutedEventArgs e)
    {
        e.CanExecute = !String.IsNullOrEmpty(StatusName);

    }

PS : I have no binding error in the VS debogger

Answer 1

In the binding, set UpdateSourceTrigger=PropertyChanged. With TextBox, the default is LostFocus, so you’ll get an empty string until you tab out.