Question

Expected Behavior

1. There are ComboBox and DatePicker.
2. On Selection changed of the combo box, depending on the combobox selection the DatePicker should be enabled or disabled.

How I am trying to implement

XAML code for Date Interval and Date Picker

<ComboBox ItemsSource="{Binding Source={StaticResource viewByInterval}}"
          SelectedValuePath="Value"
          SelectedItem="{Binding IntervalMode,Mode=TwoWay}" />

<DatePicker SelectedDate="{Binding EndDate,Mode=TwoWay}"
            IsEnabled="{Binding Path=EndDateEnabled[0],Mode=TwoWay}">

View Model code for changing the EndDateEnabled

public bool EndDateEnabled { get; set; }

public DateMode IntervalMode
{
    get
    {
        return _dateModeValue;
    }
    set
    {
        _dateModeValue = value;
        EndDateEnabled =  (value == DateMode.CustomDateRange);                
    }
}

I am unable to achieve the functionality.
Please advice.

Answer 1

You don’t need the [0] part (it’s a bool, not a collection), and the binding doesn’t need to be TwoWay:

IsEnabled="{Binding Path=EndDateEnabled}"

You also need to implement INotifyPropertyChanged in your ViewModel, and raise the PropertyChanged event for the EndDateEnabled property (and for all properties that your view is bound to):

private bool _endDateEnabled;
public bool EndDateEnabled
{
    get { return _endDateEnabled; }
    set
    {
        if (value != _endDateEnabled)
        {
            _endDateEnabled = value;
            OnPropertyChanged("EndDateEnabled");
        }
    }
}

Note that EndDateEnabled can also be a computed property with only a getter:

public bool EndDateEnabled
{
    get { return _dateModeValue == DateMode.CustomDateRange; }
}

In this case you need to call OnPropertyChanged("EndDateEnabled") in the DateModeValue setter, so that the binding is refreshed.