WCF and Hosting
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In this second part to a five-part series, you will learn about the WCF service and hosting. It is excerpted from chapter one of
Programming WCF Services, written by Juval Lowy (O'Reilly, 2007; ISBN: 0596526997). Copyright © 2007 O'Reilly Media, Inc. All rights reserved. Used with permission from the publisher. Available from booksellers or direct from O'Reilly Media.
Hosting
The WCF service class cannot exist in a void. Every WCF service must be hosted in a Windows process called the host process. A single host process can host multiple services, and the same service type can be hosted in multiple host processes. WCF makes no demand on whether or not the host process is also the client process. Obviously, having a separate process advocates fault and security isolation. It is also immaterial who provides the process or what kind of a process is involved. The host can be provided by IIS, by the Widows Activation Service (WAS) on Windows Vista, or by the developer as part of the application.
A special case of hosting is in-process hosting, or in-procfor short, where the service resides in the same process as the client. The host for the in-proc case is, by definition, provided by the developer.
IIS Hosting
The main advantage of hosting a service in the Microsoft Internet Information Server (IIS) web server is that the host process is launched automatically upon the first client request, and you rely on IIS to manage the life cycle of the host process. The main disadvantage of IIS hosting is that you can only use HTTP. With IIS5, you are further restricted to having all services use the same port number.
Hosting in IIS is very similar to hosting a classic ASMX web service. You need to create a virtual directory under IIS and supply a .svc file. The .svc file functions similar to an .asmxfile, and is used to identify the service code behind the file and class. Example 1-2 shows the syntax for the .svc file.
Example 1-2. A .svc file
<%@ ServiceHost
Language = "C#"
Debug = "true"
CodeBehind = "~/App_Code/MyService.cs"
Service = "MyService"
%>
You can even inject the service code inline in the .svc file, but that is not advisable, as is the case with ASMX web services.
When you use IIS hosting, the base address used for the service always has to be the same as the address of the .svcfile.
Using Visual Studio 2005
You can use Visual Studio 2005 to generate a boilerplate IIS-hosted service. From the File menu, select New Website and then select WCF Service from the New Web Site dialog box. This causes Visual Studio 2005 to create a new web site, service code, and matching .svcfile. You can also use the Add New Item dialog to add another service later on.
The Web.Config file
The web site config file (Web.Config) must list the types you want to expose as services. You need to use fully qualified type names, including the assembly name, if the service type comes from an unreferenced assembly:
<system.serviceModel>
<services>
<service name = "MyNamespace.MyService">
...
</service>
</services>
</system.serviceModel>
Next: Self-Hosting >>
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 This article is excerpted from chapter one of Programming WCF Services, written by Juval Lowy (O'Reilly, 2007; ISBN: 0596526997). Check it out today at your favorite bookstore. Buy this book now.
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