Skip to main content

MVVM and MVP pattern(s) as applicable to SilverLight


There could be more to these design patterns and its applicability in SilverLight, however this article is only intended to present and overview and high-level understanding of how to get started in SilverLight application patterns.

SilverLight implements SOLID design guidelines along with a MVVM or MVP design pattern.
Figure shown below  depicts the comparison of approaches followed in MVVM and MVP pattern.




MVVM pattern can follow two approaches

1.       View First: The view is responsible for creating an instance of a ViewModel, via databinding to a static resource or setting the data context in the code-behind file.
  • Databinding approach

UserControl.Resources
local:SampleViewModel x:Key=”ViewModel” /
UserControl.Resources
                Grid DataContext=”{Binding Path=Object,
Grid is bound to object that is obviously in Model.


  • Code Behind approach
 this.DataContext = new SampleViewModel();

2.       View-Model first: The ViewModel creates an instance of the view and sets its data context.
This is usually done using an Inversion of Control Container like MEF, PRISM etc.
(This  article is only an exploration of design patterns in use in silverlight)
Both these approaches have their own pros and cons that I am not going to discuss here. For the time it’s your decision based on requirement as to which approach you want to follow.

Event Broker Pattern:
The normal way to use an event is for one class to subscribe to the events of another class. This approach works great when each class has direct access to the other and only one class can trigger an event. 

However, in more advanced scenarios one or more classes may need to send the same event or be notified by events without subscribing directly to the caller event.

Events can be treated as another type of dependency and instead of subscribing directly to an event, a container (Event Broker) could be used to manage the subscribers and publishers of an event. This is  exactly what is done in IOC /Dependency injection .
When an event occurs, the Event Broker would be responsible for notifying all subscribers that an event occurred.

Let’s consider a practical example of  handling the closing of an application.
Normal Scenario:  The application needs to loop through each control on the screen to check to see if its needs to be saved before applications closes.
Event Broker Pattern Scenario:
Event Broker handles notification to each control, to save itself. Isn’t his a better approach.

Hope this was helpful.

Till Next we connect……

Happy reading……

Labels:

Comments

Post a Comment

Popular posts from this blog

Asp.Net 4.0: An Overview-Part-III

This is the last post in the series which will explore the following new features of ASP.Net 4.0  Performance Monitoring for Individual Applications in a Single Worker Process Web.config File Refactoring Permanently Redirecting a Page Expanding the Range of Allowable URLs Performance Monitoring for Individual Applications in a Single Worker Process It is a common practice to host multiple ASP.NET applications in a single worker process, In order to increase the number of Web sites that can be hosted on a single server. This practice results in difficulties for server administrators to identify an individual application that is experiencing problems. ASP.NET 4 introduces new resource-monitoring functionality introduced by the CLR. To enable this functionality, following XML configuration snippet is added to the aspnet.config configuration file.(This file is located in the directory where the .NET Framework is installed ) <?xml version="1.0" encoding="UTF-8"
Post a Comment
Read more

WCF-REST Services-Part-II

HOW REST is implemented in WCF Part-I of the series explored the REST conceptually and this post will explore how REST is implemented in WCF. For REST implementation in WCF, 2 new attributes namely WebGetAttribute and WebInvokeAttribute are introduced in WCF along with a URI template mechanism that enables you to declare the URI and verb to which each method is going to respond. The infrastructure comes in the form of a binding ( WebHttpBinding ) and a behavior ( WebHttpBehavior ) that provide the correct networking stack for using REST. Also, there is some hosting infrastructure help from a custom Service¬Host ( WebServiceHost ) and a ServiceHostFactory ( WebServiceHostFactory ). How WCF Routes messages WCF routes network messages to methods on instances of the classes defined as implementations of the service. Default behavior ( Dispatching ) for WCF is to do this routing based on the concept of action. For this dispatching to work, an action needs to be present in ev
Post a Comment
Read more

SOLID principles -Code Samples and Free Ebook

I planned to write code samples for SOLID principle implementations, however I am a firm believer of " NOT RE-INVENTING THE WHEEL ", when all you need is use the wheels and make a new CAR. Going by the ideology, I have found an excellent  SOLID principles FREE -Ebook ( covering all aspects of SOLID design principles, with Code sample). This book is an excellent visual aid to remember these principles, as it uses Motivational posters for explaining SOLID design principles. One additional advantage to the above mentioned book is the Code-Refactoring ebook . Both of these books can be downloaded from this EBOOK download Link Both of these books can be downloaded form here. Hope this book proves useful... Till next we connect.... Happy Learning..
Post a Comment
Read more