How to set up data binding for group radio button in Silverlight?

Question

Sliverlight provides radio button with GroupName to group radiobutton together with only one option from mutiple choice. It's like:

<RadioButton GroupName="Option" Content="Option 1"></RadioButton>
<RadioButton GroupName="Option" Content="Option 2"></RadioButton>
<RadioButton GroupName="Option" Content="Option 3"></RadioButton>

then in VM, I have only one property for this option,say it's MyChoice

public int MyChoice {get; set;}

then how to setup data binding for this case between UI and VM?

Answer 1

Used a converter to convert bools to an int:

On Xaml, asssuming options map to 1,2,3 on your MyChoice property:

    <RadioButton GroupName="Option" Content="Option 1"
                 IsChecked="{Binding Path=MyChoice, Converter={StaticResource RadioButtonToIntConverter}, 
        ConverterParameter=1}"/>
    <RadioButton GroupName="Option" Content="Option 2"
                 IsChecked="{Binding Path=MyChoice, Converter={StaticResource RadioButtonToIntConverter}, 
        ConverterParameter=2}"/>
    <RadioButton GroupName="Option" Content="Option 3"
                 IsChecked="{Binding Path=MyChoice, Converter={StaticResource RadioButtonToIntConverter}, 
        ConverterParameter=3}"/>

In the converter, noting that I did not add any cast protection:

public class RadioButtonToIntConverter:IValueConverter 
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var para = System.Convert.ToInt32(parameter);
        var myChoice = System.Convert.ToInt32(value);
        return para == myChoice;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var para = System.Convert.ToInt32(parameter);
        var isChecked = System.Convert.ToBoolean(value);
        return isChecked ? para : Binding.DoNothing;
    }
}

Also you'd better to implement INotifyPropertyChanged in you ViewModel.

Answer 2

Hi you will have to create three properties of type bool and bind to IsChecked property of RadioButton

<StackPanel>
        <RadioButton GroupName="Option" Content="Option 1" IsChecked="{Binding MyChoice1}"></RadioButton>
        <RadioButton GroupName="Option" Content="Option 2" IsChecked="{Binding MyChoice2}"></RadioButton>
        <RadioButton GroupName="Option" Content="Option 3" IsChecked="{Binding MyChoice3}"></RadioButton>
    </StackPanel>

ViewModel

        public class ViewModel:INotifyPropertyChanged
    {
        bool myChoice1;

        public bool MyChoice1
        {
            get { return myChoice1; }
            set { 
                myChoice1 = value;
                Notify("MyChoice1");
            }
        }
        bool myChoice2;

        public bool MyChoice2
        {
            get { return myChoice2; }
            set
            {
                myChoice2 = value;
                Notify("MyChoice2");
            }
        }
        bool myChoice3;

        public bool MyChoice3
        {
            get { return myChoice3; }
            set
            {
                myChoice3 = value;
                Notify("MyChoice3");
            }
        }

        public void Notify(string propName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propName));

        }
        public event PropertyChangedEventHandler PropertyChanged;
    }