History of Distributed Applications
Monolithic applications gave way to applications built with components using COM • Desktop COM gave way to distributed COM (DCOM) • DCOM evolved into COM+ and integrated with Microsoft Transaction Server • .NET components can use enterprise Services to leverage COM+ • .NET remoting consists of a client and remote objects hosted on a remote server • Client can access remote objects as if they were local • Enterprise Services and .NET Remoting require client components and data to be on same network • Web Services enable you to pass as XML over Internet(Sample object Access Protocol(SOAP) defines structure of XML message client and services pass)
Service Oriented Architecture
• A service is a program that performs a task and that you can interact with through well-defined message • A service-oriented application consists of loosely coupled services that communicate through message and contracts(Client dose not instantiate the service) • Shift from remotely invoking components to passing message between services(Evolution of the development model for building distributed applications)
Principles of Service Orientation
Boundaries are explicit
• Services communicate by sending message across their boundary • All communication occurs through message
Services are autonomous
• You build, manage and version services independently • You can change a service without affecting clients as long as clients can continue sending and receiving the same message
Services share contracts and schema
• Contracts describe the message services can send and receive • Schemas define how the client and service construct the message they exchange
Compatibility is policy based
• Services can define the circumstances under which clients can communicate with them
What’s Wrong with What we Have?
Too many ways to create distributed applications
• Web services (SOA) • Enterprise Services, .NET Remoting (not SOA)
Which should you use and when?
• Do you need interoperability? • Are you going over the Internet or over TCP? • Are you accessing services internally or externally?
How easy is it to change from one to another?
WCF to the Rescue
• WCF provides unified programming model for building service oriented applications • One model whether communication is internal or external • Same service can be exposed over multiple protocols without duplicating effort or switching technologies
WCF vs Web Services
• Send message via not only HTTP , but also TDP and other protocols • Send messages using formats other than SOAP • Representational state transfer(REST) and plain Old XML(POX) • Host service on hosts other than a web server • Built-in support for transactions and reliable sessions • Built-in support for managing configurations , tracing and logging messages
Windows Communication Foundation(WCF)
• Unified programming model for building service oriented applications • Next generation of distributed applications and Web services • Part of .NET Framework 3.0 and 3.5 • Consists of a runtime and classes in • System.ServiceModel namespace
Let’s go bulid are first very sample WCF service:
1. Click Create new Project 2. Select WCF node 3. Select WCF Service Library 4. Wite name HelloWorldService
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5.Click OK.
Visual Studio created Project, and added
Sysytem.ServiceModel in Refrences.
Get Code
IService1
// NOTE: If you change the interface name "IService1" here, you must also update the reference to "IService1" in App.config.
[ServiceContract]
public interface IService1
{
[OperationContract]
String SayHello(String yourName);
}
// NOTE: If you change the class name "Service1" here, you must also update the reference to "Service1" in App.config.
public string SayHello(String yourName)
{
return String.Format("Hello {0}", yourName);
}
Build Solution and Start Debugging.
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Double click (sayHello())
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Write your name and click Invoke:
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