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Windows Communication Foundation and Web Services

Windows Communication Foundation and Web Services. WCF (Introduction). It’s Microsoft’s current inter-machine communication foundation used to integrate HTTP requests and responses Web Services Messaging Lower-level TCP/IP Ajax / REST services And everything else. WCF Fundamentals.

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Windows Communication Foundation and Web Services

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  1. Windows Communication Foundation and Web Services

  2. WCF (Introduction) • It’s Microsoft’s current inter-machine communication foundation used to integrate • HTTP requests and responses • Web Services • Messaging • Lower-level TCP/IP • Ajax / REST services • And everything else

  3. WCF Fundamentals • Simply put, it’s a set of APIs used to send messages between services and clients • It’s based on messages (HTTP, MSMQ, …) • Messages are sent between endpoints • Messages are sent using a transport protocol • HTTP / TCP …

  4. WCF Model (1)

  5. WCF Model (2)

  6. WCF Model (Contracts) • Contracts describe the precise format of messages • This is done using SOAP (or other protocol) • The service contract defines the interface to the outside world • We are talking about the format of • Function calls • Parameters • Return types • These are message signatures • The programming model defines how we write the code to do all of this

  7. WCF Model (Contract)Request-Reply • Request-Reply services • This is the default type of service • Clients make a request for service (synchronously or asynchronously) • Clients receive a response • Duplex services

  8. WCF Model (Contract)One Way • In a One-Way service, the client sends a request but does not expect a response • To detect errors, create two One-Way service contracts

  9. WCF Model (Contract)Duplex • Both endpoints can send messages independently • These are implemented using the idea of a callback • To implement, create two interfaces • The first is the one-way client interface • The second is the callback contract • Refer to http://msdn.microsoft.com/en-us/library/ms731064(v=vs.110).aspx

  10. WCF Model (Service Runtime) • This layer defines the behavior of the runtime service (server configuration) • We configure the service runtime using behaviors • There is much detail here beyond the scope of this course

  11. WCF Model (Service Runtime) • How many messages are processed at a time • InstanceContextMode / ConcurrencyMode • How many instances of a server can run (singleton) • InstanceContextMode • Threading and reentrancy • ConcurrencyMode

  12. WCF Model (Messaging) • Transport channels are of two types • Transport channels send and receive messages • TCP, HTTP, MSMQ • Protocol channels implement the messaging protocols • http

  13. WCF Model (Hosting) • Simply put, it’s where the application runs (is hosted) • Might be IIS or WAS

  14. WCF Model (Hosting)

  15. WCF Model (Hosting)

  16. WCF Model (Hosting - IIS) • This is the easiest way to host your service • IIS treats the service as an ASP.NET Web Site • If you are using IIS6, then only HTTP and HTTPS are supported • You can create a self-hosted console application that listens for requests at a particular port • We can also host through Azure Services ( I have no idea how to do this)

  17. WCF and Web Services • WCF has changed the .net picture of Web Services • They used to be a standalone product type etc… • They are now just another service within the context of WCF

  18. The Goal of Web Services • Supply a standard means for e-commerce applications to communicate using different hardware and software platforms • Supply a way for legacy applications to communicate • Provide a universal way to discover the available services and the methods supplied by a particular service so that any consumer can call those methods

  19. Logical Web Service Model

  20. Calling Web Service Methods (Illustration)

  21. Web Service Vendors • IBM – WebSphere Studio Application Developer • SAP – SAP Web Application Server • SUN – Sun ONE Web Services Platform Developer Edition • And of course Microsoft and Visual Studio .NET • Others are likely to follow • No matter the vendor, Web services will always work the same way • Any consumer should work with any provider

  22. Web Service Protocols • Web services provide a hardware and software agnostic way to call remote functions and return data from those remote functions • Protocols • HTTP is the message transfer agent • Simple Object Access Protocol (SOAP) • Web Service Description Language (WSDL)

  23. SOAP • Encapsulates an XML document for the purpose of serialization • SOAP messages are exchanged between providers and consumers • SOAP is a message envelope containing an XML document • Consumers send SOAP requests to providers • Requests are method calls serialized into an XML document • Providers send responses to consumers in the form of another XML document • All of this happens behind the scenes and is not that significant to the developer

  24. WSDL • A WSDL document fully describes a Web service • All methods are defined • Method signatures are also defined • A WSDL document is a well-formed and valid XML document • A WSDL document is almost always generated automatically • They become very complex very quickly • .NET uses the WSDL document along with Intellisense technology to display member calling conventions (signature prototypes)

  25. C# Attributes • C# Attributes allow metadata to be compiled into an application • They are used for many purposes – Web services being one • Reflection

  26. Creating A Web Service • Create a new Web side using the WCF Service project type

  27. Web Service Lifecycle • Design the service contract • Implement the service contract • This is done via attributes • Configure the service endpoints • Host the service • Build client applications

  28. Web Service Implementation (Steps) • Declare the members of the interface that will be implemented in the .svc file • Implement those members in the corresponding class

  29. Service Contract • A service exposes one or more service operations • A ServiceContract defines the types of messages used in a conversation • A ServiceOperation defines the messages themselves

  30. Service Contract (Example 1)

  31. Service Contract (Example 2) • Use a class instead of creating an interface and implementing that interface

  32. Data Contract • Simply put, simple types do not require a data contract. Complex types do • Serializable parameters do not require a data contract • A DataContract describes a type that will be serialized by the service • A DataMember describe the members of the DataContracttype

  33. Data Contract (Example 1)

  34. Configure Service Endpoints (1) • Communication occurs through service endpoints and four properties • Address of the endpoint • A binding that specifies how a client can communicate with the endpoint • A contract the defines the allowable operations • Local implementation details

  35. Configure Service Endpoints (2) • We can configure endpoints via • Code • In the config (web.config) file

  36. Configure Service Binding (1) • Most bindings are provided with WCF • Use BasicHttpBinding for most Web services

  37. Host the Service • IIS must be installed on the server

  38. Compiling the Service • The service is compiled the same way as any other .NET app. • If you run it, you see a “special” test client window • The code is generated by .NET itself

  39. Test Service (Illustration 1)

  40. Test Service (Illustration 2)

  41. Creating the Test Client • Create a WPF or Windows forms application • Insert the template code created by Svcutil.exe into this project • While the service is running locally, add a service reference • In a production app, you will have this URL • Change the name of the endpoint in app.config

  42. Adding the Service Reference (Example)

  43. Changing the endpoint • Rename the end point in the app.config file

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