Method overloading is the process of implementing Polymorphism in Object-Oriented Programming. A method can be overloaded on the basis of type of parameters, number of parameters, and an order of parameters.
As we know, WCF code is always coded on OOP's based programming language so that it does support method overloading.
Service Interface
[ServiceContract] public interface ITest { [OperationContract] string TestMethod(int para1,int para2); //Initail method [OperationContract] string TestMethod(string para1, string para2); //Overloading on the basis of type of parameters. [OperationContract] string TestMethod(int para1, string para2); //Overloading on the basis of an order of parameters. [OperationContract] string TestMethod(int para1, string para2,double para3); //Overloading on the basis of the numbers of parameters }
Service implementation
public class Test : ITest { public string TestMethod(int para1, int para2) { return "TestMethod1"; } public string TestMethod(string para1, string para2) { return "TestMethod2"; } public string TestMethod(int para1, string para2) { return "TestMethod3"; } public string TestMethod(int para1, string para2, double para3) { return "TestMethod4"; } }
Issues of method overloading in WCF
Once test the above code on WCF test client, it will throw an error contract mismatch because of the WSDL that does n't allow to create duplicate methods for clients.
Error: Cannot obtain Metadata from http://localhost:61489/Test.svc If this is a Windows (R) Communication Foundation service to which you have access, please check that you have enabled metadata publishing at the specified address. For help enabling metadata publishing, please refer to the MSDN documentation at http://go.microsoft.com/fwlink/?LinkId=65455.WS-Metadata Exchange Error URI: http://localhost:61489/Test.svc Metadata contains a reference that cannot be resolved: 'http://localhost:61489/Test.svc'. The server did not provide a meaningful reply; this might be caused by a contract mismatch, a premature session shutdown or an internal server error. HTTP GET Error URI: http://localhost:61489/Test.svc There was an error downloading 'http://localhost:61489/Test.svc'. The request failed with the error message:--<html> <head> <title>The type 'MethOverWCF.Test', provided as the Service attribute value in the ServiceHost directive, or provided in the configuration element system.serviceModel/serviceHostingEnvironment/serviceActivations could not be found
Solution of method overloading issue in WCF
By adding unique operationcontract behavior, we can be achieved method overloading in WCF. OperationContract has the Name property that exposes the WCF methods to WSDL Schemas.
[ServiceContract] public interface ITest { [OperationContract(Name="Method1")] string TestMethod(int para1,int para2); //Initail method [OperationContract(Name = "Method2")] string TestMethod(string para1, string para2); //Overloading on the basis of type of parameters. [OperationContract(Name = "Method3")] string TestMethod(int para1, string para2); //Overloading on the basis of an order of parameters. [OperationContract(Name = "Method4")] string TestMethod(int para1, string para2,double para3); //Overloading on the basis of the numbers of parameters }
Creating Client and Consuming overloaded WCF service methods
In WCF client, all service methods are called by exact same name as define in the OperationContract but method overloaded methods are called by their attribute name. In the given sample code has four different attributes (Method1, Method2, Method3, and Method4) which are exposed by overloaded TestMethod of WCF.
using WCFConsoleClentApp.MyTest; namespace WCFConsoleClentApp { class Program { static void Main(string[] args) { TestClient client = new TestClient(); string callMethod1 = client.Method1(1, 1); string callMethod2 = client.Method2("Test", "Test"); string callMethod3 = client.Method3(1, "Test"); string callMethod4 = client.Method4(1, "Test", 3.5); } } }