Using Unity Dependency Injection with WCF services

Question

I have the following after doing some research on other questions:

MyServiceHost:

public class MyServiceHost : ServiceHost
{
    public MyServiceHost(IUnityContainer container, Type serviceType, params Uri[] baseAddresses)
        : base(serviceType, baseAddresses)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        foreach (var cd in this.ImplementedContracts.Values)
        {
            cd.Behaviors.Add(new DependencyInjectionInstanceProvider(container));
        }
    }
}

DependencyInjectionInstanceProvider:

public class DependencyInjectionInstanceProvider : IInstanceProvider, IContractBehavior 
{     
    private readonly IUnityContainer container;      
    public DependencyInjectionInstanceProvider(IUnityContainer container)     
    {         
        if (container == null)         
        {             
            throw new ArgumentNullException("container");         
        }          

        this.container = container;     

    }      

    #region IInstanceProvider Members      

    public object GetInstance(InstanceContext instanceContext, Message message)     
    {         
        return this.GetInstance(instanceContext);     
    }      

    public object GetInstance(InstanceContext instanceContext)     
    {         
        var serviceType = instanceContext.Host.Description.ServiceType;         
        return this.container.Resolve(serviceType);     
    }      

    public void ReleaseInstance(InstanceContext instanceContext, object instance)    
    {        
        this.container.Teardown(instance);     
    }      

    #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 

} 

MyServiceHostFactory:

    public class MyServiceHostFactory : ServiceHostFactory
{
    private readonly IUnityContainer container;     
    protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses) 
    { 
        return new MyServiceHost(this.container, serviceType, baseAddresses); 
    }
}

Email Service with an attempted Constructor Injection:

public class EmailValidator : IEmailValidator
{
    private IFakeDAL fakeDAL;

    public EmailValidator(IFakeDAL fakeDAL)
    {
        this.fakeDAL = fakeDAL;
    }

    public bool ValidateAddress(string emailAddress)
    {
        Console.WriteLine("Validating: {0}", emailAddress);

        string pattern = @"^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*@(([0-9a-zA-Z])+([-\w]*[0-9a-zA-Z])*\.)+[a-zA-Z]{2,9})$";
        return Regex.IsMatch(emailAddress, pattern);
    }
}

My Console Host to start the Service:

static void Main(string[] args)
    {
        Type serviceType = typeof(EmailValidator);
        Uri serviceUri = new Uri("http://localhost:8080/");

        MyServiceHostFactory shf = new MyServiceHostFactory();
        ServiceHost host = shf.CreateServiceHost(serviceType, serviceUri);
        //ServiceHost host = new ServiceHost(serviceType, serviceUri);
        host.Open();

My problem resides in the console host logic. The CreateServiceHost call has a syntax error due to the first argument expecting a Constructor string and not a Type. Which I don't understand since it does accept a Type parameter. In addition to that I don't understand where I should be mapping IFakeDAL to a concrete class. Can I do that in an app.config file or should I register that somewhere else?

Answer 1

ServiceHostFactory is for hosting in IIS. In self hosting you should use your derived ServiceHost directly. Here you have whole example including Unity configuration.

Answer 2

I´m using the following classes in my windows service to create WCF services and inject dependencies to it using unity.

UnityInstanceProvider:

internal class UnityInstanceProvider : IInstanceProvider {

    private readonly IUnityContainer container;
    private readonly Type contractType;

    public UnityInstanceProvider(IUnityContainer container, Type contractType) {
        this.container = container;
        this.contractType = contractType;
    }

    public object GetInstance(InstanceContext instanceContext) {
        return GetInstance(instanceContext, null);
    }

    public object GetInstance(InstanceContext instanceContext, Message message) {
        return container.Resolve(contractType);
    }

    public void ReleaseInstance(InstanceContext instanceContext, object instance) {
        container.Teardown(instance);
    }
}

UnityServiceBehavior:

public class UnityServiceBehavior : IServiceBehavior {

    private readonly IUnityContainer container;

    public UnityServiceBehavior(IUnityContainer container) {
        this.container = container;
    }

    public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) {
    }

    public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters) {
    }

    public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) {
        foreach (ChannelDispatcher channelDispatcher in serviceHostBase.ChannelDispatchers) {
            foreach (EndpointDispatcher endpointDispatcher in channelDispatcher.Endpoints) {
                if (endpointDispatcher.ContractName != "IMetadataExchange") {
                    string contractName = endpointDispatcher.ContractName;
                    ServiceEndpoint serviceEndpoint = serviceDescription.Endpoints.FirstOrDefault(e => e.Contract.Name == contractName);
                    endpointDispatcher.DispatchRuntime.InstanceProvider = new UnityInstanceProvider(this.container, serviceEndpoint.Contract.ContractType);
                }
            }
        }
    }
}

UnityServiceHost:

public class UnityServiceHost : ServiceHost {

    private IUnityContainer unityContainer;

    public UnityServiceHost(IUnityContainer unityContainer, Type serviceType)
        : base(serviceType) {
        this.unityContainer = unityContainer;
    }

    protected override void OnOpening() {
        base.OnOpening();

        if (this.Description.Behaviors.Find<UnityServiceBehavior>() == null) {
            this.Description.Behaviors.Add(new UnityServiceBehavior(this.unityContainer));
        }
    }
}

With this classes you can do the following (The configuration of services is done in .config):

UnityContainer container = new UnityContainer();
UnityServiceHost serviceHost = new UnityServiceHost(container, typeof("Type of Service to host"));
serviceHost.Open();

Answer 3

The CreateServiceHost method expects an array of Uri instances, so try this instead:

ServiceHost host = shf.CreateServiceHost(serviceType, new[] { serviceUri });

You can map interfaces to types in either XML or code, but I'd recommend code, since XML has too high a maintenance overhead.

The Main method is an excellent Composition Root, but if you want to configure the container at that level, you'll need to pass it from the Main method to MyServiceHostFactory - which is perfectly fine when you host the service in a console application, but will not work if you want to host it in IIS, where MyServiceHostFactory should be the Composition Root, since IIS requires a default constructor.