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What are contracts in WCF?


In WCF, all services expose contracts. The contract is a platform-neutral and standard way of describing what the service does.
WCF defines four types of contracts.
Service contracts:
Describe which operations the client can perform on the service. There are two types of Service Contracts.
ServiceContract - This attribute is used to define the Interface.
OperationContract - This attribute is used to define the method inside Interface.
interface IMyContract
string MyMethod( );
class MyService : IMyContract
public string MyMethod( )
return "Hello World";
Data contracts:
Define which data types are passed to and from the service. WCF defines implicit contracts for built-in types such as int and string, but we can easily define explicit opt-in data contracts for custom types.
There are two types of Data Contracts.
DataContract - attribute used to define the class
DataMember - attribute used to define the properties.
class Contact
public string FirstName;
public string LastName;
If DataMember attributes are not specified for a properties in the class, that property can't be passed to-from web service.
Fault contracts:
Define which errors are raised by the service, and how the service handles and propagates errors to its clients.

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