In this article, Mahesh Sabnis shows how to establish communication between two Views of the same Module (intra-module) or two Views of different Modules in Silverlight 4 and Prism 4.
Source: Dot Net Curry
A lot of times, we think of using patterns in our Silverlight applications for implementing loose-coupling, modularity, reusability etc. Using MVVM/Prism can make this possible. Prism 4 has provided several features for implementing such type of applications. Typically Modularity is one of the most important segments in Prism. A Module contains application specific logic, models, views etc. We can say that our Prism enabled Silverlight application consist of several such Modules. In such cases, based upon a business requirement, it is necessary to establish communication between two Views of the same Module (intra-module) or two Views of different Modules. So the question is how we can achieve this.