WPF binding ComboBox to enum (with a twist)

Question

Well the problem is that I have this enum, BUT I don't want the combobox to show the values of the enum. This is the enum:

public enum Mode
    {
        [Description("Display active only")]
        Active,
        [Description("Display selected only")]
        Selected,
        [Description("Display active and selected")]
        ActiveAndSelected
    }

So in the ComboBox instead of displaying Active, Selected or ActiveAndSelected, I want to display the DescriptionProperty for each value of the enum. I do have an extension method called GetDescription() for the enum:

public static string GetDescription(this Enum enumObj)
        {
            FieldInfo fieldInfo =
                enumObj.GetType().GetField(enumObj.ToString());

            object[] attribArray = fieldInfo.GetCustomAttributes(false);

            if (attribArray.Length == 0)
            {
                return enumObj.ToString();
            }
            else
            {
                DescriptionAttribute attrib =
                    attribArray[0] as DescriptionAttribute;
                return attrib.Description;
            }
        }

So is there a way I can bind the enum to the ComboBox AND show it's content with the GetDescription extension method?

Thanks!

Answer 1

I would suggest a DataTemplate and a ValueConverter. That will let you customize the way it's displayed, but you would still be able to read the combobox's SelectedItem property and get the actual enum value.

ValueConverters require a lot of boilerplate code, but there's nothing too complicated here. First you create the ValueConverter class:

public class ModeConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter,
        CultureInfo culture)
    {
        return ((Mode) value).GetDescription();
    }
    public object ConvertBack(object value, Type targetType, object parameter,
        CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

Since you're only converting enum values to strings (for display), you don't need ConvertBack -- that's just for two-way binding scenarios.

Then you put an instance of the ValueConverter into your resources, with something like this:

<Window ... xmlns:WpfApplication1="clr-namespace:WpfApplication1">
    <Window.Resources>
        <WpfApplication1:ModeConverter x:Key="modeConverter"/>
    </Window.Resources>
    ....
</Window>

Then you're ready to give the ComboBox a DisplayTemplate that formats its items using the ModeConverter:

<ComboBox Name="comboBox" ...>
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Converter={StaticResource modeConverter}}"/>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

To test this, I threw in a Label too, that would show me the actual SelectedItem value, and it did indeed show that SelectedItem is the enum instead of the display text, which is what I would want:

<Label Content="{Binding ElementName=comboBox, Path=SelectedItem}"/>