WCF is meant for designing and deploying distributed applications under service-oriented architecture (SOA) implementation. WCF is designed using service oriented architecture principles to support distributed computing where services have remote consumers. Clients can consume multiple services; services can be consumed by multiple clients. Services are loosely coupled to each other. Services typically have a WSDL interface (Web Services Description Language) that any WCF client can use to consume the service, regardless of which platform the service is hosted on. WCF implements many advanced Web services (WS) standards such as WS-Addressing, WS-ReliableMessaging and WS-Security. With the release of .NET Framework 4.0, WCF also provides RSS Syndication Services, WS-Discovery, routing and better support for REST services.
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WCF Data Services (formerly known as "ADO.NET Data Services") is a component of the .NET Framework that enables developers to create services that use the Open Data Protocol (OData) to expose and consume data over the Web or intranet by using the semantics of representational state transfer (REST). OData exposes data as resources that are addressable by URIs. Data is accessed and changed by using standard HTTP verbs of GET, PUT, POST, and DELETE. OData uses the entity-relationship conventions of the Entity Data Model to expose resources as sets of entities that are related by associations.
WCF Data Services can expose data that originates from various sources as OData feeds. Visual Studio tools make it easier for developers to create an OData-based service by using an ADO.NET Entity Framework data model. Developers can also create OData feeds based on common language runtime (CLR) classes and even late-bound or un-typed data.
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WCF RIA Services simplifies the development of n-tier solutions for Rich Internet Applications (RIA), such as Silverlight applications. A common problem when developing an n-tier RIA solution is coordinating application logic between the middle tier and the presentation tier. To create the best user experience, you want your RIA Services client to be aware of the application logic that resides on the server, but you do not want to develop and maintain the application logic on both the presentation tier and the middle tier. RIA Services solves this problem by providing framework components, tools, and services that make the application logic on the server available to the RIA Services client without requiring you to manually duplicate that programming logic. Developers can create a RIA Services client that is aware of business rules and know that the client is automatically updated with latest middle tier logic every time that the solution is re-compiled.
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