Book Image

MVVM Survival Guide for Enterprise Architectures in Silverlight and WPF

Book Image

MVVM Survival Guide for Enterprise Architectures in Silverlight and WPF

Overview of this book

MVVM (Model View View Model) is a Microsoft best practices pattern for working in WPF and Silverlight that is highly recommended by both Microsoft and industry experts alike. This book will look at the reasons for the pattern still being slow to become an industry standard, addressing the pain points of MVVM. It will help Silverlight and WPF programmers get up and running quickly with this useful pattern.MVVM Survival Guide for Enterprise Architectures in Silverlight and WPF will help you to choose the best MVVM approach for your project while giving you the tools, techniques, and confidence that you will need to succeed. Implementing MVVM can be a challenge, and this book will walk you through the main issues you will come across when using the pattern in real world enterprise applications.This book will help you to improve your WPF and Silverlight application design, allowing you to tackle the many challenges in creating presentation architectures for enterprise applications. You will be given examples that show the strengths and weaknesses of each of the major patterns. The book then dives into a full 3 tier enterprise implementation of MVVM and takes you through the various options available and trade-offs for each approach. During your journey you will see how to satisfy all the demands of modern WPF and Silverlight enterprise applications including scalability, testability, extensibility, and blendability.Complete your transition from ASP.NET and WinForms to Silverlight and WPF by embracing the new tools of these platforms, and the new design style that they allow for. MVVM Survival Guide for Enterprise Architectures in Silverlight and WPF will get you up to speed and ready to take advantage of this powerful new presentation platform.
Table of Contents (21 chapters)
MVVM Survival Guide for Enterprise Architectures in Silverlight and WPF
Credits
Foreword
About the Authors
About the Reviewer
www.PacktPub.com
Preface
MVVM Frameworks
Index

Validations and dependency properties


DependencyProperty supports the validation of the value being assigned to it via a callback method. Whenever the property value is set, the WPF and Silverlight runtimes can call a callback to check if its value is valid. The callback method simply needs to return true for valid or false for invalid to take advantage of this feature. This feature is especially useful for custom controls and element adapters, which are implemented as DependencyObject. The callback is specified at the time that the dependency property is registered with the WPF runtime. The callback is passed as one of the parameters to the Register static method on the DependencyProperty class, as shown in the following code:

public static DependencyProperty Register(
  string name,
  Type propertyType,
  Type ownerType,
  PropertyMetadata typeMetadata,
  ValidateValueCallback validateValueCallback
)

Where ValidateValueCallback is as follows:

public delegate bool ValidateValueCallback(
...