Hi,
Based on my understanding, the problem your are experiencing could be related to the fact that the Prism's IncokeCommandAction is located in the Microsoft.Practices.Prism.Interactivity assembly and not in the main Prism assembly. Hence in your XAML you could try adding the following reference:
(...)
xmlns:prism="http://www.codeplex.com/prism" xmlns:prismInt="clr-namespace:Microsoft.Practices.Prism.Interactivity;assembly=Microsoft.Practices.Prism.Interactivity" xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity> <StackPanel> <TextBox> <i:Interaction.Triggers> <i:EventTrigger EventName="KeyUp"> <prismInt:InvokeCommandAction Command="{Binding MyCommand}" /> </i:EventTrigger> </i:Interaction.Triggers> </TextBox>
(...)
I hope you find this handy,
Agustin Adami
http://blogs.southworks.net/aadami