Building State of the art presentation tiers

Nauzad Kapadianauzadk@quartzsystems.com

Key Objectives

• Importance of the presentation tier and overview of technologies available

• Guidelines for designing presentation tiers

• Discuss the issues commonly faced in presentation tiers

• Present solutions and workarounds

Importance of the presentation tier

ASP.Net

Silverlight

Flash

Windows Presentation Foundation

Windows Forms

Flex

HTML 5

User Experience

Silverlight OOBXBAP

The MVVM Pattern

View

• Contains the User Interface

• The Face of the application

View Model

• Drives the View

• Provides all the data required by the view, in the format that it requires

Model

• Provides the business logic for the PT

• Acts like a gateway between the PT and the middle -tier

Testability

• Problem–What is the easiest way to test my

presentation tiers

• Solution– Use the MVVM pattern

Separation of concerns and reuse

• Problem–Want to free the UI from the logic that

drives it– Re-use of presentation tiers in different

environments with minimal effort

• Solution– Use the MVVM pattern.

DEMOApplication design using the MVVM pattern

Caching - guidelines

• Carefully choose the right data for caching

• Chose the appropriate location for the cache

• Design a cache refresh and updation strategy

Caching

• Problems– How do I synchronize my cache across

multiple servers across a farm– How do I cache data on the client in a

non-obstructive manner

• Solutions– Use Velocity® for web-farm level

cachine– Use the IsolatedStorage area on the

client-side

DEMOUsing the Isolated Storage Area

Validation guidelines

• Design a non-intrusive, but fool-proof validation strategy

• Display error messages prominently• Do not perform excessive validations

Validation

• Problem– How do I provide some generic rules which can

be re-used in multiple places– How do I centralize all my validation logic for a

single entity– How do I control when the validation rules are

fired

• Solutions– Use Validation Rules for generic validations– Use IDataErrorInfo for centralizing validation logic– Use ErrorProvider pattern for more control

DEMOIDataErrorInfo and ErrorProviders

Exception Management guidelines

• Design a centralized exception management strategy

• Log Exceptions• Display appropriate and generic error

messages• Do not use exceptions to control

program flow• Do not re-throw the same exception

// BAD WAY// ... search for Productif ( dr.Read() ==0 ) // no record found, ask to create{

//this is an example of throwing an unnecessary exception because//nothing has gone wrong and it is a perfectly acceptable situationthrow( new Exception(“Product Not found"));

}

// GOOD WAY// ... search for Productif ( dr.Read() ==0 ){ // no record found, ask to create

return false;}

Navigation guidelines

• Allow navigation within your application to happen in a easy consistent manner

• Consider access rules and security trimming while implementing navigation

• Navigation elements should reflect the state of the application.

Navigation

• Problem– How do I keep my UI controls and

navigation elements in sync with the current state of my application

• Solution– Use the Controller Pattern– Use the Commanding Pattern

DEMOThe Commanding Pattern

Localization guidelines

• Build localization support right in the beginning

• Design the UI keeping in mind that string sizes may vary significantly for the same content in different languages

Localization

• Problem– How do I localize my UI in multiple

languages– How do I facilitate the addition of

“language packs” to my application

• Solutions– Use .resx files

DEMOLocalizing applications

Composite application guidelines

• Decide how modules will fit into the overall application

• Decide how to discover modules• Decide on a DI container• Determine the communication

strategy between modules

Composite Applications

• Problem– How do I build a modular application– How do I discover modules at runtime– How do I enable loosely coupled

communication between modules

• Solutions– Use PRISM– Use a Dependency Injection framework

like MEF or Unity

DEMODI using MEF

UI Responsiveness guidelines

• Do not block the UI thread ever• Show the progress of a long running

operation• Consider giving the user the chance

to cancel a long running operation• Reduce the start-up time of modules• Pre-initialize commonly-used

modules and views

UI Responsiveness

• Problem– How do I ensure that my UI is not blocked during

a long running operation– How do I allow the user the cancel a long-running

operation– How do I improve the responsive-ness of my UI

• Solution– Use background threads for long running

operations– Use Task Parallel Library or ThreadPools– Use Caching

ResourcesSoftware Application

Developers

http://msdn.microsoft.com/

Infrastructure Professionals

http://technet.microsoft.com/

msdnindia technetindia @msdnindia @technetindia

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