Geeks With Blogs
Josh King AKA JK

Welcome to my fantastic blog, and very first blog post! In my first post I thought I would share my first experience with the .NET dynamic data type, while doing some Silverlight binding.

The scenario is I have a View, ViewModel and Model project. My Model project gets data from a WCF service, and sets the appropriate properties in the ViewModel. There's an ObservableCollection property in the ViewModel bound to a DataGrid in the View.

The data in the ObservableCollection can be filtered through a search within the application. I want a Label control to display the results of the search, such as "Your search returned 34 results". So I did something crazy! Binding the updated ObservableCollection to the Label. This could have been done with a separate property, being updated from the set of the ObservableCollection, but that approach was too boring.

So you may ask, how does a Label element bound to an ObservableCollection display text? Through the magic of binding converters...



<conversion:CollectionConverter x:Key="collectionConversion"></conversion:CollectionConverter>

<sdk:Label Content="{Binding WorkOrders, Converter={StaticResource collectionConversion}}" Foreground="Blue" Cursor="Hand"></sdk:Label>

WorkOrders is the ObservableCollection property from the ViewModel class, which implements INotifyPropertyChanged.

Converter Class:

namespace SampleBuddy
public class CollectionConverter : IValueConverter
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
string text = "Your search returned ";
dynamic collection = value;

if (collection != null)
text += collection.Count.ToString() + " results";
return text;

public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{return value;}

To better learn how to implement the converter, check out this article.

So I was able to bind to an existing property, and update the display whenever the collection changes from the ViewModel. Since I couldn't cast the object, because it was referenced from the ViewModel and not the View, the dynamic data type came in very handy.

Hope you enjoyed my first post.


Posted on Wednesday, April 6, 2011 8:49 AM Silverlight | Back to top

Comments on this post: Silverlight Binding with the dynamic Data Type

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