Question

I have for example property like this:

private string foobar;

    public string Foobar
    {
        get
        {
            return this.foobar;
        }

        set
        {
            if (value != this.foobar)
            {
                // here I want to check if value is correct
                if(value != something)
                {
                   this.foobar = value;
                   this.NotifyPropertyChanged("Foobar");
                 }
                 else
                 {
                    value = null;
                    this.foobar = null;
                    this.NotifyPropertyChanged("Foobar");
                 }
            }
        }
    }

Property is binded (MVVM) to Listview :
SelectedItem="{Binding Foobar, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}
.

And when user changes value in list, selecteditem is changed and value is set in setter. I code is ok, when user selected incorrect value, to value and foobar null is assigned. But in WPF still selected value is displayed. When I set breakpoint in getter I can see that it return null too. How to refresh WPF to clear selected value in listview ? It shoud be empty like at the begin.

Thanks

Answer 1

The problem with your code is that you want to override value assigned by binding in your setter method. This will not work because control will not update on next property change for simple reason that it has invoked it by setting property. To implement validation on your values try this build in mechanism.