What is the difference between ServiceContract, OperationContract, and DataContract?

Question

ICSM Computer · Answer

In WCF, ServiceContract, OperationContract, and 
DataContract serve distinct purposes in defining how a service operates and communicates with clients. Here's a clear breakdown:
1. ServiceContract
Purpose: Defines the interface (contract) for a WCF service — i.e.,
what operations the service exposes to clients.Applied To: An interface or class.
Example:
[ServiceContract]
public interface ICalculator
{
    [OperationContract]
    int Add(int x, int y);
}
2. OperationContract
Purpose: Marks individual methods in the service contract that are exposed as
operations to clients.Applied To: Methods inside a ServiceContract.
Example:
[OperationContract]
int Subtract(int x, int y);
Only methods marked with OperationContract are accessible to clients.
3. DataContract
Purpose: Defines the structure of complex data types (objects) that are passed in and out of service operations.Applied To: Classes or structs used as parameters or return types.
Example:
[DataContract]
public class Person
{
    [DataMember]
    public string Name { get; set; }
    [DataMember]
    public int Age { get; set; }
}
Only members marked with DataMember are serialized for transport.
Summary Table
Attribute
Applied To
Purpose
ServiceContract
Interface/class
Defines the service and its public interface
OperationContract
Method
Marks the method as a callable operation
DataContract
Class/struct
Defines complex data structures
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What is the difference between ServiceContract, OperationContract, and DataContract?

ICSM Computer

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1 Answers

1. ServiceContract

2. OperationContract

3. DataContract

Summary Table

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Attribute	Applied To	Purpose
`ServiceContract`	Interface/class	Defines the service and its public interface
`OperationContract`	Method	Marks the method as a callable operation
`DataContract`	Class/struct	Defines complex data structures