How do I pass values to the constructor on my wcf service?
You'll need to implement a combination of custom ServiceHostFactory
, ServiceHost
and IInstanceProvider
.
Given a service with this constructor signature:
public MyService(IDependency dep)
Here's an example that can spin up MyService:
public class MyServiceHostFactory : ServiceHostFactory
{
private readonly IDependency dep;
public MyServiceHostFactory()
{
this.dep = new MyClass();
}
protected override ServiceHost CreateServiceHost(Type serviceType,
Uri[] baseAddresses)
{
return new MyServiceHost(this.dep, serviceType, baseAddresses);
}
}
public class MyServiceHost : ServiceHost
{
public MyServiceHost(IDependency dep, Type serviceType, params Uri[] baseAddresses)
: base(serviceType, baseAddresses)
{
if (dep == null)
{
throw new ArgumentNullException("dep");
}
foreach (var cd in this.ImplementedContracts.Values)
{
cd.Behaviors.Add(new MyInstanceProvider(dep));
}
}
}
public class MyInstanceProvider : IInstanceProvider, IContractBehavior
{
private readonly IDependency dep;
public MyInstanceProvider(IDependency dep)
{
if (dep == null)
{
throw new ArgumentNullException("dep");
}
this.dep = dep;
}
#region IInstanceProvider Members
public object GetInstance(InstanceContext instanceContext, Message message)
{
return this.GetInstance(instanceContext);
}
public object GetInstance(InstanceContext instanceContext)
{
return new MyService(this.dep);
}
public void ReleaseInstance(InstanceContext instanceContext, object instance)
{
var disposable = instance as IDisposable;
if (disposable != null)
{
disposable.Dispose();
}
}
#endregion
#region IContractBehavior Members
public void AddBindingParameters(ContractDescription contractDescription, ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
{
}
public void ApplyClientBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, ClientRuntime clientRuntime)
{
}
public void ApplyDispatchBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, DispatchRuntime dispatchRuntime)
{
dispatchRuntime.InstanceProvider = this;
}
public void Validate(ContractDescription contractDescription, ServiceEndpoint endpoint)
{
}
#endregion
}
Register MyServiceHostFactory in your MyService.svc file, or use MyServiceHost directly in code for self-hosting scenarios.
You can easily generalize this approach, and in fact some DI Containers have already done this for you (cue: Windsor's WCF Facility).
You can simply create and instance of your Service
and pass that instance to the ServiceHost
object. The only thing you have to do is to add a [ServiceBehaviour]
attribute for your service and mark all returned objects with [DataContract]
attribute.
Here is a mock up:
namespace Service
{
[ServiceContract]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
public class MyService
{
private readonly IDependency _dep;
public MyService(IDependency dep)
{
_dep = dep;
}
public MyDataObject GetData()
{
return _dep.GetData();
}
}
[DataContract]
public class MyDataObject
{
public MyDataObject(string name)
{
Name = name;
}
public string Name { get; private set; }
}
public interface IDependency
{
MyDataObject GetData();
}
}
and the usage:
var dep = new Dependecy();
var myService = new MyService(dep);
var host = new ServiceHost(myService);
host.Open();
I hope this will make life easier for someone.
Mark's answer with the IInstanceProvider
is correct.
Instead of using the custom ServiceHostFactory you could also use a custom attribute (say MyInstanceProviderBehaviorAttribute
). Derive it from Attribute
, make it implement IServiceBehavior
and implement the IServiceBehavior.ApplyDispatchBehavior
method like
// YourInstanceProvider implements IInstanceProvider
var instanceProvider = new YourInstanceProvider(<yourargs>);
foreach (ChannelDispatcher dispatcher in serviceHostBase.ChannelDispatchers)
{
foreach (var epDispatcher in dispatcher.Endpoints)
{
// this registers your custom IInstanceProvider
epDispatcher.DispatchRuntime.InstanceProvider = instanceProvider;
}
}
Then, apply the attribute to your service implementation class
[ServiceBehavior]
[MyInstanceProviderBehavior(<params as you want>)]
public class MyService : IMyContract
The third option: you can also apply a service behavior using the configuration file.