Message
exchange pattern describes how client and WCF service exchange message to each
other.
You know
that WCF data is in XML or JSON format and WCF Client and service exchange
messages in XML or JSON format.
There
are three types of exchange patterns :
1.
Request/Response
2. One way
3. Duplex
Request-reply pattern:
In the
request-reply pattern, a client application sends a message to a WCF service
and then waits for a reply. This is the classic and most commonly used message
exchange pattern in WCF.
In this
exchange pattern if the service doesn't respond to the client then the client
will receive a TimeoutException.
Example:
[ServiceContract(ConfigurationName
= "IProductWebService")]
public interface
IEcommerceWebService
{
/// <summary>
/// Product price information
updating
/// </summary>
// specifies the
request-reply message pattern
[OperationContract(IsOneWay=false)]
bool UpdatePriceList(ProductPrice
Price);
}
One-way pattern:
one-way message exchange pattern, a client
application sends a message to a WCF service but the service does not send a
reply message to the client. You can use this pattern when a client requests
the service take an action but does not need to wait for a reply.
This pattern
doesn’t supports output parameters, by-reference parameters and return value to
an operation, otherwise you will receive an InvalidOperationException.
Example:
[ServiceContract(ConfigurationName
= "IProductWebService")]
public interface
IEcommerceWebService
{
/// <summary>
/// Save new price
information
/// </summary>
[OperationContract(IsOneWay
= true)]
void
SavePriceData(BasicPrice Price);
}
Duplex pattern:
In the
request/reply and one-way message exchange patterns, only the client can
initiate communication. In the duplex pattern, both the client and the service
can initiate communication. The client calls a method of the service. The service
can then use a client callback to call a method in the client. You can use this
pattern when you want the service to send a notification or alert to the client
after the client has called the service.
Example:
//associate service contract with service contract using call back
attribute
[ServiceContract(CallbackContract = typeof(IProductServiceCallBack))]
public interface
IProductService
{
[OperationContract]
Product GetInfo();
}
public interface
IProductServiceCallBack
{
[OperationContract]
void SaveProduct(Product
BasicProduct);
}
Please explain with example