Configure Web API:

Web API supports code based configuration. It cannot be configured in web.config file. We can configure Web API to customize the behaviour of Web API hosting infrastructure and components such as routes, formatters, filters, DependencyResolver, MessageHandlers, ParamterBindingRules, properties, services etc.

We created a simple Web API project in the Create Web API Project section. Web API project includes default WebApiConfig class in the App_Start folder and also includes Global.asax as shown below.

Configure Web API
Global.asax

public class WebAPIApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        GlobalConfiguration.Configure(WebApiConfig.Register);
        
        //other configuration
    }
}

WebApiConfig

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {

        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        // configure additional webapi settings here..
    }
}

Web API configuration process starts when the application starts. It calls GlobalConfiguration.Configure(WebApiConfig.Register) in the Application_Start method. The Configure() method requires the callback method where Web API has been configured in code. By default this is the static WebApiConfig.Register() method.

As you can see above, WebApiConfig.Register() method includes a parameter of HttpConfiguration type which is then used to configure the Web API. The HttpConfiguration is the main class which includes following properties using which you can override the default behaviour of Web API.

Property Description
DependencyResolver Gets or sets the dependency resolver for dependency injection.
Filters Gets or sets the filters.
Formatters Gets or sets the media-type formatters.
IncludeErrorDetailPolicy Gets or sets a value indicating whether error details should be included in error messages.
MessageHandlers Gets or sets the message handlers.
ParameterBindingRules Gets the collection of rules for how parameters should be bound.
Properties Gets the properties associated with this Web API instance.
Routes Gets the collection of routes configured for the Web API.
Services Gets the Web API services.

Visit MSDN to learn about all the members of HttpConfiguration.

Learn how to configure Web API routes in the next section.