This Article explains you to how to use Message Contracts in Windows communication Foundation...
Message Contract…..?
• Message Contract are useful when you need a control on the layout of your SOAP Message by adding specific headers and footers to a message...
• They describe the flow of SOAP Messages sent to and from a service and also enables you to Inspect and control all the details in the SOAP Header and body...
• Though WCF automatically manages the message. On some critical issue, we also require control over the SOAP message format. In that case WCF provides Message Contract to customize the message as per requirement.
• Message contract can be applied to type using Message Contract attribute. Custom Header and Body can be included to message using 'Message Header' and 'MessageBodyMember'atttribute as shown below
How they Differ from Data Contracts…..?
Data contracts are used to define the data structure. Messages that are simply a .NET type, let’s say in form of POCO (plain old CLR object), and generate the XML for the data you want to pass. Whereas
Message contracts are preferred when we need to “control” the layout of your message (the SOAP message); by adding specific headers/footer/etc. to a message.
Note:-
There are some certain rules to be noticed while applying the Message Contract
1. Only one parameter can be used in service Operation while using message contract type as a parameter
2. Service Operation will accept only message contract as return type.it doesn’t accept any other data types
Let’s look into the sample Implementation:-
Employee Data Contract:-
Add new Employee Data Contract to handle the Employee related info by adding new class to Service library. Add below code to the class and reference to System.Runtime.Serialization
[DataContract]
public class Employee
{
// [DataMember (EmitDefaultValue=false,Order=1,Name="Name",IsRequired=true)]
[DataMember]
public string FirstName { get; set;}
// [DataMember(EmitDefaultValue = true, Order=0,IsRequired=false)]
[DataMember]
public string LastName { get; set; }
// [DataMember(EmitDefaultValue = false,Order=2)]
// [IgnoreDataMember]
[DataMember]
public string Designation{ get; set; }
Request Message Contract:-
Create a new Message Contract for request by adding new class to Service library. Name it as Employee Request. Add reference to System.ServiceModel
[MessageContract]
public class EmployeeRequest
{
[MessageHeader]
string EmployeeId;
}
// [IgnoreDataMember]
Response Message Contract:-
Now Create a Message Contract for response.
[MessageContract]
public class EmployeeResponse
{
[MessageBodyMember]
public Employee eobj;
}
Adding Service Contract:-
Add a service contract to handle customer message request and response.
public interface IService1
{
[OperationContract]
[FaultContract(typeof(string))]
EmployeeResponse GetInfo(EmployeeRequest Req);
}
Implementation of I Service:-
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;
namespace Sample_MessageContract
{
// NOTE:You can use the "Rename" command on the "Refactor" menu to
change the class name "Service1" in code, svc and config file together.
// NOTE: In order to launch WCF Test Client for testing this service, please select
Service1.svc or Service1.svc.cs at the Solution Explorer and start debugging.
public class Service1 : IService1
{
private const string EmployeeId = "533";
public EmployeeResponse GetInfo(EmployeeRequest Req)
{
if (Req.EmployeeId != EmployeeId)
{
string v = "Invalid User ID";
throw new FaultException<string>(v);
}
EmployeeResponse ER = new EmployeeResponse();
ER.eobj = new Employee();
ER.eobj.FirstName = "Rama";
ER.eobj.LastName = "Sagar";
ER.eobj.Designation = "Software Developer";
return ER;
}
}
}
Now Host the Service and invoke the service as shown below
Now take a Sample client application to test the Message Contract
Add an aspx page, create a button and text box. And then add a Service Reference…The end point is created automatically as shown below
<client>
<endpoint address="http://localhost:4463/Service1.svc" binding="basicHttpBinding"
bindingConfiguration="BasicHttpBinding_IService1" contract="Sample_MessageContract_Referance.IService1" name="BasicHttpBinding_IService1" />
</client>
Now run the Application and check with the employee id
Conclusion
In this article, we examined how to implement Message Contracts .and what are the advantages of using them…..You can download the complete source code and can test it………