Configuration-Based Activation in IIS and WAS

Normally when hosting a Windows Communication Foundation (WCF) service under Internet Information Services (IIS) or Windows Process Activation Service (WAS), you must provide a .svc file. The .svc file contains the name of the service and an optional custom service host factory. This additional file adds manageability overhead. The configuration-based activation feature removes the requirement to have a .svc file and therefore the associated overhead.

Configuration-Based Activation

Configuration-based activation takes the metadata that used to be placed in the .svc file and places it in the Web.config file. Within the<serviceHostingEnvironment> element there is a <serviceActivations> element. Within the <serviceActivations> element are one or more <add> elements, one for each hosted service. The <add> element contains attributes that let you set the relative address for the service and the service type or a service host factory. The following configuration example code shows how this section is used.


Each <add> element must specify a service or a factory attribute. Specifying both service and factory attributes is allowed.

    <add relativeAddress="MyServiceAddress" service="Service" factory="MyServiceHostFactory"/>

With this in the Web.config file, you can place the service source code in the App_Code directory of the application or a complied assembly in the Bin directory of the application.


  • When using configuration-based activation, inline code in .svc files is not supported.
  • The relativeAddress attribute must be set to a relative address such as "<sub-directory>/service.svc" or "~/<sub-directory/service.svc".
  • A configuration exception is thrown if you register a relative address that does not have a known extension associated with WCF.
  • The relative address specified is relative to the root of the virtual application.
  • Due to the hierarchical model of configuration, the registered relative addresses at machine and site level are inherited by virtual applications.
  • Registrations in a configuration file take precedence over settings in a .svc, .xamlx, .xoml, or other file.
  • Any ‘\’ (backslashes) in a URI sent to IIS/WAS are automatically converted to a ‘/’ (forward slash). If a relative address is added that contains a ‘\’ and you send IIS a URI that uses the relative address, the backslash is converted to a forward slash and IIS cannot match it to the relative address. IIS sends out trace information that indicates that there are no matches found.

See also