HttpContextBase.Items

When you using controller, you can easily access HttpContext property, which is not an System.Web.HttpContext, but a HttpContextBase object. This object has a handy Items dictionary, which can allowed you share data over a the whole request.

TempData of Controller

TempData is property of Controller. The TempData is used to save the state from page redirected from to the page redirected. So let say, your request is handled by controller1.method1, for some reason, it should be redirected to controller2.method2. Before the redirection take place, you can save some data in the TempData, then http status code 302 and new url are returned to browser, and browser make a new request using new url. In the new action method, the TempData can be restored. This behavior is showed in the following code in the Controller

//Controller member
protected override void ExecuteCore() {
    TempData.Load(ControllerContext, TempDataProvider);

Extension point in asp.net mvc

1. Extending route.

   Route matching is first step mvc framework, we can customize how route is matched by adding constraint, and default, and dataToken. We can implement IRouteConstraint. Here is ASP.NET MVC Tip #30 – Create Custom Route Constraints

2. Extending IRouteHandler

   When we register route, by default the route handler is MvcRouteHandler. We can create a class implmenting IRouteHandler, of we can sub class MvcRouteHandler

3. Exending MvcHandler

   MvcHandler is IHttpHandler, we can substitute with a MvcHandler sub class, or a complete new IHttpHandler , or override MvcHandler's ProcessRequest method. We can override ProcessRequest(HttpContextBase httpContext) method.

How a view is found

There are some confusing names here. ViewResult is kind of ActionResult. It is return by an object of Controller class. ViewResult uses VewEngineCollection, a collection of IViewEngine, to find a ViewEngineResult. ViewEngineResult may or may not contain an IView. IView is implemented by ViewPage, ViewUserControl.

After a action result is returned from the action method, if it is ViewResult. The render method will find an ViewEngineResult through ViewEngineCollection object. The following code show how ViewEngineCollection finds ViewEngineResult, ViewEngineCollection enumerate all the ViewEngine to fine ViewEngineResult.

Context data in asp.net mvc

Along the asp.net mvc stack, there are lots context data being passing around. The first context data is passed into MvcRouteHandler by the System.Web.Routing.UrlRoutingModule.