DYNAMIC STATE STORAGE:UNDERSTANDING THE ASP.NET

PROVIDER MODEL

Miguel A. Castro

miguel.castro@idesign.net

ineta

.NET Architect, Developer, & Trainer Microsoft MVP ASP Insider Member of the INETA Speakers Bureau Conference Speaker Creator of CodeBreeze In IT business since 1986

Your Speaker

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Agenda

• What is a Provider?

• The [ASP.NET] Provider Model

• The Config File

• Identifying the Need for Swappable State Storage

• Designing & Developing the Swappable State Storage Provider

• Summary

What is a Provider?• Based on the Strategy Pattern (GoF)

• Allows the separation of definition and implementation + ability to swap implementations

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Provider Definition(interface or abstract

class)

Concrete class 1 Concrete class 2

Config decides

which to use.

The ASP.NET Provider Model

• Designed by the ASP.NET team

• Part of System.Web.dll• Used by many features of ASP.NET

• Membership, Roles, Profile, WebPart, Personalization, Session, Logging, etc.

• Not just for ASP.NET

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Config-file Provider Sections

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<membership defaultProvider="{defaultProvider}"> <providers> <add name="{provider name}“ type="{.Net type}" .../> <add name="{provider name}“ type="{.Net type}" .../> </providers> </membership>

The Membership Provider

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Membership.CreateUser

Factory Class Command

Static Constructor:•Read Web.Config file•Determine what Provider to use•Instantiate Provider and cast to Abstraction•Call CreateUser in provider

The Membership Provider

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Membership Object Model

Membership

MembershipProvider

SqlMembershipProvider

Static Factory Class

Abstraction

Provider Class

The Membership Provider

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<membership defaultProvider=“AspMembershipProvider"> <providers>

<clear /><add name="AspMembershipProvider“

type=“System.Web.Security. SqlMembershipProvider“ connectionStringName="connStr“ requiresUniqueEmail="true”

… other attributes … </providers></membership>

Swappable State StorageRequirements

• Ability to swap out method of state storage on-the-fly.– Session– Application– Cache– Cookies

• Ability to define more than one state-storage provider.

Swappable State StorageDesign

• Configuration section handler.– Config model follows standard provider

config model

• Static factory class for entry point.

• Provider Base class defines public interface.

• One provider implementation class for each type of storage.

Swappable State StorageDesign

• Data:– Ability to isolate storage by provider name

– Ability to isolate storage by user• (using the Session ID)

– Key and Value used for storage/retrieval

• Behavior:– Store an item

– Retrieve a stored item

Swappable State Storage

• Some data is static for ALL usage– Information described in previous slides

• Some data is different for EACH usage– Key used for storage– Value being stored

• Static data can be fed using configuration

• Dynamic data fed into method arguments

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Swappable State Storage Static Attributes

• isolateProvider– Uses name of the provider in the storage key– Allows two instances of same provider type to

store using same key

• isolateUser– Uses session ID in the storage key– Allows two users to store using same key– Important in Application and Cache

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Configuration Section

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<configSections> <sectionGroup name="system.web"> <section name="stateStorage" type="WebFormLibrary. StateStorageSection, WebFormLibrary"/> </sectionGroup> </configSections>

Configuration Section

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<stateStorage defaultProvider="SessionStorageProvider"> <providers> <clear/> <add name=" SessionStorageProvider " type="WebFormLibrary. SessionStateStorageProvider, WebFormLibrary" isolateProvider="true" /> <add name="ApplicationStorageProvider" type="WebFormLibrary. ApplicationStateStorageProvider, WebFormLibrary" isolateUser="true" isolateProvider="true" /> </providers> </stateStorage>

Custom Config-Section Class

• Inherits from ConfigurationSection• Properties:

• DefaultProvider:string• Providers:ProviderSettingsCollection

• Decorated with ConfigurationProperty• Rest of configuration definition handled by ProviderSettingsCollection type

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The Provider’s Definition

• Abstract class

• Inherits from ProviderBase• Defines fields that will come in from config

• Defines properties exposed by all implementations

• Defines abstract methods

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Concrete Classes(Session)

• Inherits from provider definition class• Overrides Initialize (ProviderBase)

• Config-section (<provider>) attributes received as NameValueCollection object.

• Provider-specific _Fields (defined here) and those defined in base class are filled.

• If expected attribute is not found, throw ProviderException

• Allowed attributes are removed from collection and collection is checked for anything left over.

• Abstract methods implemented

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The Factory Class

• Point of entry

• Static constructor reads all defined providers and makes provider determination from config information

• Duplicates provider’s methods for entry

• Exposes a collection of all providers addressable by name

• Exposes default provider

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Writing Providers

• Can be defined in separate assemblies

• Similar to the Session-State provider

• May use same, different, more, or less attributes than other providers– Has its own Initialize method implementation

• Implement abstract methods– Same, similar, or different than other providers

• Assembly needs to be accessible by host

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Writing Providers

• Application State Provider– Like Session but uses Application variable

• Cache State Provider– Like Session but uses Cache variable

• Cookie State Provider– Like the others but must serialize and

deserialize values before storage and retrieval– Cookies only store string values

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Using The Providers

• Define one or more in the config• Define one as the default provider• Use the default provider

• Use the StateStorage factory class to store and/or retrieve values

• Use a specific provider• Define a variable of the base class-type• Set to an element of StateStorage.Providers

using provider name as key

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Summary

• Provider model can accommodate a terrific plug-in architecture for many features of your application

• Familiar & proven pattern

• Can be used outside of ASP.NET• Need to reference System.Web.dll

• The ability to swap state storage can come in very handy

References

www.dotnetdude.comwww.steelbluesolutions.com25

• Programming Microsoft ASP.NET Advanced Topics• Dino Esposito – Microsoft Press

• Professional ASP.NET 4.0 with C# or VB}• Mathew MacDonald - APress