How do I pass values to the constructor on my wcf service?

Question

I would like to pass values into the constructor on the class that implements my service.

However ServiceHost only lets me pass in the name of the type to create,

Answer 1

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.

Answer 2

This was a very helpful solution - especially for someone who is a novice WCF coder. I did want to post a little tip for any users who might be using this for an IIS-hosted service. MyServiceHost needs to inherit WebServiceHost, not just ServiceHost.

public class MyServiceHost : WebServiceHost
{
    public MyServiceHost(MyService instance, Type serviceType, params Uri[] baseAddresses)
        : base(instance, baseAddresses)
    {
    }
}

This will create all the necessary bindings, etc for your endpoints in IIS.