Skip to main content

Binding Enum with DescriptionAttribute in WPF

Binding an enumeration to a ComboBox can be done in several ways. In most cases you don't want to display the value itself, but a more user friendly description. One common approach is to use the DescriptionAttribute on the Enum values to supply a description for each value. This is all possible in a very MVVM friendly way.

First step is to add the DescriptionAttribute to the values of the enumeration.

public enum MyValues
{
    [Description("First value")]
    First,

    [Description("Second value")]
    Second
}

To retrieve the description from the enum we use a simple extension method. This method returns the value of the DescriptionAttribute if it exists, otherwise the string representation of the enum value is returned.

public static string GetDescription(this Enum value)
{
    var fieldInfo = value.GetType().GetField(value.ToString());
    var attribute = fieldInfo.GetCustomAttributes(typeof(DescriptionAttribute), false).FirstOrDefault() as DescriptionAttribute;

    return attribute != null ? attribute.Description : value.ToString();
}

With this extension method it is really easy to write a generic enum description converter to use where ever an enum value is presented to the user. But the more interesting case is where we want to present the enumeration in a ComboBox or a similar control. To accomplish this you can use a MarkupExtension. (Please note that this code is stripped from all type validation and such to be easier to read.)

public class EnumExtension : MarkupExtension
{
    private readonly Type _enumType;

    public EnumExtension(Type enumType)
    {
        _enumType = enumType;
    }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        return (from object enumValue in Enum.GetValues(_enumType)
                select new EnumMember {Value = enumValue, Description = ((Enum)enumValue).GetDescription()}).ToArray();
    }

    public class EnumMember
    {
        public string Description { get; set; }
        public object Value { get; set; }
    }
}

The DescriptionAttribute together with these extensions gives us a really neat way of populating the values of an enum into a ComboBox.

<ComboBox SelectedValue="{Binding MyValue}"
          ItemsSource="{Binding Source={my:EnumExtension {x:Type MyValues}}}"
          DisplayMemberPath="Description" SelectedValuePath="Value" />

Comments

Post a Comment

Popular posts from this blog

Moving to the cloud - part 1

I cannot with words describe the hype around the cloud today, and of course I had to join the croud. I have transferred all my applications, files and services to the cloud. I thought I would share some of the experiences and difficulties I have hit during my jourey. These are the steps I have performed in order to complete my move to the cloud: Most of my files are safely stored with  Dropbox . E-mail accounts for stodell.se  were moved from service provider to  Google Apps . The Cornball was moved from service provider to  Windows Azure och SQL Azure . This blog was moved from Wordpress at a service provider to  Google's Blogger . Even though  Loopia has been a great service provider during many years I have now been able to cancel all my services except the domain hosting with them. The replacement being free services and the Azure capacity that is included in the MSDN subscription.

Binding a HTML-formatted string to a WPF WebBrowser control

Sometimes there is a need to display a HTML formatted string in a WPF application. There are a couple of ways to do this, but the most stright forward is to use a WebBrowser control and the NavigateToString method. This approach has one big flaw, you cannot use binding to a string out of the box, but I found a great solution through Stack Overflow which adds a bindable property to the  WebBrowser  control using  NavigateToString . The following class is all that is needed to add that behavior. A new depencency property named Html is introduced to the  WebBrowser  and the proper change action is performed in the OnHtmlChanged method. public class BrowserBehavior { public static readonly DependencyProperty HtmlProperty = DependencyProperty.RegisterAttached( "Html", typeof(string), typeof(BrowserBehavior), new FrameworkPropertyMetadata(OnHtmlChanged)); [AttachedPropertyBrowsableForType(typeof(WebBrowser))] public static string GetHtml(WebBrowser bro

Getting started with Silverlight

In my work with the Cornball as my first Silverlight project I have had to solve a huge amount of problems which turned out to be quite a high threshold before I could get started with the development for real. Not the least in the difference between a WinForms application and a Silverlight application. In this post I will mention a couple of the things i encountered. Splash Screen/Preloader The builtin preloader in Silverlight does not look too bad, but it is definately more fun to create a custom preloader to fit with the rest of the application. I choose to create a very simple but functional preloader. First I had to include all the images as resources in the application for the preloader to actually have a purpose. By adding the images to the project and select Resource as Build Action the images will be included in the XAP-file. To show the images in the application, something of the following will do. XAML <Image Name="Card" Source="/SilverlightApplicatio