How use injection in wcf - wcf

Question

I have two classes implementing a contract at a service which are consumed from a factory on the client like shown below.
[ServiceContract]
public interface MyInterface {
void DoSomething()
}
public class A : MyInterface {
public void DoSomething(){
"Hi I'm A"
}
}
public class B : MyInterface {
public void DoSomething(){
"Hi I'm B"
}
}
public class MyFactory <TMyInterface> {
void DoSomething(){
TMyInterface.DoSomething()
}
}
The client must remain the same. My question is how can I choose at the server side which implementation of MyInterface to use, by passing the type parameter using .config file in WCF
I read other post but I don't understand yet :(

Answer 1

It is possible to do it, and there are a few ways to do it.
One possibility is to create a "routing" service which will contain the "public" address which the client always talks to. This routing service can then, based on some configuration, redirect the call to the appropriate "real" service.
Another way is to actually have a process which starts both services, but their addresses are defined in config. If you use the same binding and the same contract (which is the case), then you can "flip-flop" the service address when you want to change the service which will receive the calls from the client. For example, this configuration directs the requests to the endpoint at "http://machine-name:8000/Service" to service A. Notice that, since you define service hosts for both services, you actually need to have a base address for service B as well - in this case I used named pipes, which cannot be accessed via different machines.
<system.serviceModel>
<services>
<service name="A">
<host>
<baseAddresses>
<add baseAddress="http://machine-name:8000/Service"/>
</baseAddresses>
</host>
<endpoint address="" binding="basicHttpBinding" contract="MyInterface" />
</service>
<service name="B">
<host>
<baseAddresses>
<add baseAddress="net.pipe://localhost/ServiceBackup"/>
</baseAddresses>
</host>
<endpoint address="" binding="netNamedPipeBinding" contract="MyInterface" />
</service>
</services>
</system.serviceModel>
when you want to change the address for B, you'd then swap the addresses.
<system.serviceModel>
<services>
<service name="A">
<host>
<baseAddresses>
<add baseAddress="net.pipe://localhost/ServiceBackup"/>
</baseAddresses>
</host>
<endpoint address="" binding="netNamedPipeBinding" contract="MyInterface" />
</service>
<service name="B">
<host>
<baseAddresses>
<add baseAddress="http://machine-name:8000/Service"/>
</baseAddresses>
</host>
<endpoint address="" binding="basicHttpBinding" contract="MyInterface" />
</service>
</services>
</system.serviceModel>
The hosting program would look like this:
public static void HostServices()
{
ServiceHost hostA = new ServiceHost(typeof(A));
ServiceHost hostB = new ServiceHost(typeof(B));
hostA.Open();
hostB.Open();
Console.WriteLine("Press ENTER to close");
Console.ReadLine();
hostA.Close();
hostB.Close();
}
Now, if your services are hosted in IIS (webhost), then it's a little harder. Since the "normal" activation requires a .svc file to be part of the endpoint address, and each .svc file is associated with a single class, the address for A would be something like http://machine-name/services/a.svc while the address for B would be something like http://machine-name/services/b.svc. So what you'd need to do in this case is to create a custom ServiceHostFactory, and use the ASP.NET Routes integration to create a .svc-less URL for your service. Then you'd use something similar to the previous example to decide which service will be activated.