A Custom ServiceHostFactory

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Introduction

There are two main ways to host a WCF Service. One approach is to write a server, typically as a console app. The other is to use a managed hosting environment (e.g., Internet Information Services (IIS) or Windows Process Activation Service (WAS)).

When using the second approach, the creation of the services hosts is done automatically, based on a configuration file (Web.config), where the endpoints are defined. But, there are situations when the service hosts must be created programmatically.

In this tip, I'll explain how to customize the host creation when hosting the service in a managed hosting environment.

Background

I spent some time searching for a way to create endpoints without using a Web.config file when hosting a service using IIS. And, all that I found was a small example (two lines!) in MSDN. So, here I will show a more complete solution.

First, we need to familiarize with some classes.

Framework 3.5

• WebServiceHostFactory: "A factory that provides instances of WebServiceHost in managed hosting environments where the host instance is created dynamically in response to incoming messages". In other words: IIS and WAS use this class to create Service Hosts.
• WebServiceHost: Instances of this class are created by WebServiceHostFactory.

Using the Code

First, we need to write a class that derives from WebServiceHostFactory. Let's call it MyWebServiceHostFactory. In this class, all we need to do is to override the CreateServiceHost method.

In this method, we create the host the way we want.

protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses)
{
    ServiceHost host = new ServiceHost(serviceType, baseAddresses);

    foreach (Uri address in baseAddresses)
    {
        WSHttpBinding b = new WSHttpBinding(SecurityMode.Message);

        b.Name = serviceType.Name;

        host.AddServiceEndpoint(serviceType.GetInterfaces()[0], b, address);
    }
    return host;
}

Now, it's time to tell the host environment to use our HostFactory. It's very simple. We just need to set the property Factory in the .svc file, as shown below:

<% @ ServiceHost Language="C#" Service="WcfService1.Service1" 
                 Factory="WcfService1.MyWebServiceHostFactory" %>

Well done! Now, the host environment will call the MyWebServiceHostFactory.CreateServiceHost method to create the service hosts.

Points of interest

This approach allows you to host a service on IIS or WAS without configuring endpoints and bindings in the Web.config because you can create it programmatically with your custom ServiceHostFactory. Now, for example, one could load the endpoints information from a database, or from a service.

Next Step

The next step is to provide ASP.NET AJAX support to the Service Hosts created. To do so, I will write a factory that derives from WebScriptServiceHostFactory.