CODEWITHSUNDEEP
c#wpfxamldata-bindingmvvm
user1053426
user1053426

Reputation: 113

Setting IsEnabled to true or false based on property from View Model

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.

Upvotes: 0

Views: 3124

Answers (2)

Thomas Levesque
Thomas Levesque

Reputation: 292425

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.

Upvotes: 5

Charles Josephs
Charles Josephs

Reputation: 1535

There are 2 problems that I see. First, your binding to EndDateEnabled should look more like:

IsEnabled="{Binding Path=EndDateEnabled}"

The [0] isn't valid or necessary since the target of the binding is just a plan bool property. The TwoWay shouldn't apply here, I don't think, but it doesn't hurt to have it.

The backing ViewModel should implement INotifyPropertyChanged in order to notify the UI that the property has changed. The code for the EndDateEnabled property might end up looking something like:

private bool endDateEnabled = false;
public bool EndDateEnabled 
{
    get { return endDateEnabled; }
    set 
    {
        if (endDateEnabled != value)
        {
            endDateEnabled = value;
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs("EndDateEnabled"));
        }
    }
}

I did that from memory so it may not be perfect but it is the general idea.

Upvotes: 0

Related Questions