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.
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.
string MyMethod( );
class MyService : IMyContract
public string MyMethod( )
return "Hello World";
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.
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.
Define which errors are raised by the service, and how the service handles and propagates errors to its clients.
Allow the service to interact directly with messages. Message contracts can be typed or untyped, and are useful in interoperability cases and when there is an existing message format we have to comply with.
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