WPF Binding a ListBox to an enum, displaying the Description Attribute

Question

Is it possible to use the ObjectDataProvider method to bind a ListBox to an enum, and style it somehow to display the Description attriibute? If so how would one go about doing this...?

Answer 1

Yes, it is possible. This will do it. Say we have the enum

public enum MyEnum
{
    [Description("MyEnum1 Description")]
    MyEnum1,
    [Description("MyEnum2 Description")]
    MyEnum2,
    [Description("MyEnum3 Description")]
    MyEnum3
}

Then we can use the ObjectDataProvider as

xmlns:MyEnumerations="clr-namespace:MyEnumerations"

<ObjectDataProvider MethodName="GetValues"
                ObjectType="{x:Type sys:Enum}"
                x:Key="MyEnumValues">
    <ObjectDataProvider.MethodParameters>
        <x:Type TypeName="MyEnumerations:MyEnum" />
    </ObjectDataProvider.MethodParameters>
</ObjectDataProvider>

And for the ListBox we set the ItemsSource to MyEnumValues and apply an ItemTemplate with a Converter.

<ListBox Name="c_myListBox" SelectedIndex="0" Margin="8"
        ItemsSource="{Binding Source={StaticResource MyEnumValues}}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Converter={StaticResource EnumDescriptionConverter}}"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

And in the converter we get the description and return it

public class EnumDescriptionConverter : IValueConverter
{
    private string GetEnumDescription(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;
        }
    }

    object IValueConverter.Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        Enum myEnum = (Enum)value;
        string description = GetEnumDescription(myEnum);
        return description;
    }

    object IValueConverter.ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return string.Empty;
    }
}

The GetEnumDescription method should probably go somewhere else but you get the idea :)

Check GetEnumDescription as extension method.

Answer 2

Another solution would be a custom MarkupExtension that generates the items from enum type. This makes the xaml more compact and readable.

using System.ComponentModel;

namespace EnumDemo
{
    public enum Numbers
    {
        [Description("1")]
        One,

        [Description("2")]
        Two,

        Three,
    }
}

Example of usage:

<Window x:Class="EnumDemo.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:EnumDemo">

    <ListBox ItemsSource="{local:EnumToCollection EnumType={x:Type local:Numbers}}"/>

</Window>

MarkupExtension implementation

using System;
using System.ComponentModel;
using System.Linq;
using System.Windows.Markup;

namespace EnumDemo
{
    public class EnumToCollectionExtension : MarkupExtension
    {
        public Type EnumType { get; set; }

        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            if (EnumType == null) throw new ArgumentNullException(nameof(EnumType));

            return Enum.GetValues(EnumType).Cast<Enum>().Select(EnumToDescriptionOrString);
        }

        private string EnumToDescriptionOrString(Enum value)
        {
            return value.GetType().GetField(value.ToString())
                       .GetCustomAttributes(typeof(DescriptionAttribute), false)
                       .Cast<DescriptionAttribute>()
                       .FirstOrDefault()?.Description ?? value.ToString();
        }
    }
}

Answer 3

If you bind to the Enum, you could probably convert this to the description through an IValueConverter.

See Binding ComboBoxes to enums... in Silverlight! for a description on how to accomplish this.

See http://msdn.microsoft.com/en-us/library/system.windows.data.ivalueconverter.aspx for more information.

Answer 4

You can define a ressource file in your project (*.resx file). In this file you must define "key-value-pairs", something like this:

"YellowCars" : "Yellow Cars",
"RedCars" : "Red Cars",

and so on...

The keys are equals to your enum-entries, something like this:

public enum CarColors
{
    YellowCars,
    RedCars
}

and so on...

When you use WPF you can implement in your XAML-Code, something like this:

<ComboBox ItemsSource="{Binding Source={StaticResource CarColors}}" SelectedValue="{Binding CarColor, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Converter={StaticResource CarColorConverter}}" />
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

Then you must write your Converter, something like this:

using System;
using System.Globalization;
using System.Resources;
using System.Windows.Data;

public class CarColorConverter : IValueConverter
{
    private static ResourceManager CarColors = new ResourceManager(typeof(Properties.CarColors));

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var key = ((Enum)value).ToString();
        var result = CarColors.GetString(key);
        if (result == null) {
            result = key;
        }

        return result;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

My answer comes 7 years to late ;-) But maybe it can be used by someone else!