Asp.net mvc internals & extensibility

MVC Internals &
Extensibility

Eyal Vardi
CEO E4D Solutions LTD
Microsoft MVP Visual C#
blog: www.eVardi.com

Agenda
 Routing

 Dependency Resolver

 Controller Extensibility

 Model Extensibility

 View Extensibility

© 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: Eyal@E4D.co.il

MVC in ASP.NET


ASP.NET vs. ASP.NET MVC


MVC Execution Process
ASP.NET

IIS Routing ASP.NET
MVC 3.0


URL Routing
URL to Page
http://Domain/Path

URL to Controller

http://Domain/.../..


Routes
 A route is a URL pattern that is mapped to a
handler.
 The handler can be a physical file, such as an .aspx file in a
Web Forms application.
 A handler can also be a class that processes the request,
such as a controller in an MVC application.

protected void Application_Start() Global.asax
{
RouteTable
.Routes
.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL template
new { controller="Calc", action="Add", id=UrlParameter.Optional }
);
}


URL Patterns in MVC Applications

 {Controller} / {Action} / {id}

 Query / {queryname} / {*queryvalues}
 “*” This is referred to as a catch-all parameter.

 /query/select/bikes/onsale
 queryname = "select" , queryvalues = "bikes/onsale"


URL Routing Pipeline


Adding Constraints to Routes
 Constraints are defined by using regular
expressions string or by using objects that
implement the IRouteConstraint interface.
{
RouteTable
.Routes
.MapRoute(
"Blog",
"Posts/{postDate}",
new { controller="Blog",action="GetPosts" }
);
}
/Posts/28-12-71 => BlogController,GetPosts( “28-12-1971” )
/Post/28 => BlogController,GetPosts( “28” )
/Post/test => BlogController,GetPosts( “test” )


IRouteConstraint
{
RouteTable
.Routes
.MapRoute(
new { controller="Calc", action="Add", id=UrlParameter.Optional },
new { action = new MyRouteConstraint() }
);
}
Custom Route Constraint


Regular Expression Route
Constraint
protected void Application_Start()
{
RouteTable
.Routes
.MapRoute(
new { controller="Calc", action="Add", id=UrlParameter.Optional },
new { action = @"d{2}-d{2}-d{4}" }
);
}
Regular Expression


Route lifecycle


Routing Process

Route MvcRouteHandler MvcHandler Controller

IDependencyResolver


Custom Route
Constraint


Routing Summary
 URL Templates
 Default values
 Namespaces
 Constraint

 IRouteHandler

 RouteBase


Dependency Resolver
 Service locator for the framework.
protected void Application_Start()
{
...

DependencyResolver.SetResolver(new TraceDependencyResolver() );
}


Trace Dependency Resolver


Dependency Resolver


Controller Extensibility


Understanding Controllers
 MVC controllers are responsible for
responding to requests made against an
ASP.NET MVC website.


Controller Class


Creation of the Controller
 IControllerFactory
Responsible for determining the
controller to service the request.
 IControllerActivator
Responsible for creating the
controller
 DefaultControllerFactory has
internal class called
DefaultControllerActivator.


Creation of the Controller
Request
Routing MvcRouteHandler MvcHandler

Dependency Controller Dependency Controller
Resolver Resolver Controller
Factory Activator


How Controller
Created?


Controller Summary
 MvcHandler

 IControllerFactory

 IControllerActivator


The Action Execution
Request
Routing MvcRouteHandler MvcHandler

Factory Activator

Action Action
Invoker Method


 Once the controller has been instantiated, the
specified action has to be executed, and this
is handled by the IActionInvoker.
 If you derived your controller from the Controller class, then
this is the responsibility of an action invoker.


Built-In Action Invoker
 Finds a method that has the
same name as the requested
action.


Custom Action Name
 You can then accept an action name that
wouldn’t be legal as a C# method name.
 [ActionName("User-Registration")]
 [ActionNameSelector]


Action Method Selection
 The action invoker uses an action method
selector to remove ambiguity when selecting
an action.
 The invoker gives preference to the actions
that have selectors.


Custom Action Method Selector
 You return true from IsValidForRequest if the
method is able to process a request, and false
otherwise.


Custom Method
Selector


Handling Unknown Actions


Action Summary
 IActionInvoker

 Action Name Selector

 Action Method Selector

 Handling Unknown Actions


Model Extensibility


What Is a Model?
Model Binding
Model

Deserialization

HTML View Controller HTTP

Template


HTTP to .NET Classes

public ActionResult Index(Reservation reservation)
{
// TODO BL.
return View( reservation );
} Deserialization


HTTP to .NET Args


Model Binders
 Binders are like type converters, because they
can convert HTTP requests into objects that
are passed to an action method.


DefaultModelBinder Class
 Translate HTTP request into
complex models, including
nested types and arrays.
 URL
 Form data, Culture - Sensitive

1. Request.Form

2. RoutedData.Values
(Key,Value)
3. Request.QueryString

4. Request.Files


Model Binder Types
 ByteArrayModelBinder

 LinqBinaryModelBinder

 FormCollectionModelBinder

 HttpPostedFileBaseModelBinder

 DefaultModelBinder


Binding to Complex Types
[DisplayName("Book")] Model
public class E4DBook
{
[Display(Name = "Title")]
public string E4DTitle { get; set; }

public Reservation MyReservation { get; set; }
}

@Html.LabelFor(model => model.MyReservation.FlightNum) View
@Html.EditorFor(model => model.MyReservation.FlightNum)

Html
<label for="MyReservation_FlightNum">FlightNum</label>

<input type="text" value=""
id = "MyReservation_FlightNum"
name = "MyReservation.FlightNum" />


Specifying Custom Prefixes
Controller
public ActionResult Index(
Reservation res1 ,
[Bind(Prefix="myRes")] Reservation res2 ) { ... }

<!– First Arg --> Html
<label for="FlightNum">FlightNum</label>
<input type="text" id="FlightNum" name="FlightNum" />

...

<!– Second Arg -->
<label for="MyRes_FlightNum">FlightNum</label>
<input type="text" id="MyRes_FlightNum" name="MyRes.FlightNum" />


Bind Attribute (“View”)
 Represents an attribute that is used to provide
details about how model binding to a
parameter should occur.

[Bind(Include = "FlightNum, TravelDate)]
public class Reservation
{
public int FlightNum { get; set; }
public DateTime TravelDate { get; set; }
public int TicketCount { get; set; }
public int DiscountPercent { get; set; }
}


Bind Attribute


Binding to a String Collections
Controller
public ActionResult Index( List< string > reservation ) { ... }

Html
<input type="text" name="reservation" />


Binding to a Collections
Controller
public ActionResult Index( List<Reservation> reservation ) { ... }

<!– Option I--> Html
<input type="text" name="[0].Name" />
<input type="text" name="[1].Name" />

<!– Option II -->
<input type="hidden" name="Index" value="f1" />
<input type="text" name="[f1].Name" />

<input type="hidden" name="Index" value="f2" />
<input type="text" name="[f2].Name" />


Binding to a Dictionary
Controller
public ActionResult Index( Dictionary<Reservation> reservation ) { ... }

Html
<input type="hidden" name="[0].key" value="f1" />
<input type="text" name="[0].value.Name" />

<input type="hidden" name="[1].key" value="f2" />
<input type="text" name="[1].value.Name" />


Custom Model Binders
 ASP.NET MVC allows us to override both the
default model binder, as well as add custom
model binders.
ModelBinders.Binders.DefaultBinder = new CustomDefaultBinder();

ModelBinders.Binders.Add(
typeof(DateTime),
new DateTimeModelBinder() );


ModelBinder Attribute
 Represents an attribute that is used to
associate a model type to a model-builder
type.
public ActionResult Contact(
[ModelBinder(typeof(ContactBinder))] Contact contact )
{
ViewData["name"] = contact.Name;
ViewData["email"] = contact.Email;
ViewData["message"] = contact.Message;
ViewData["title"] = "Succes!";

return View();
}


Custom Binder


Model Summary
 Http to .NET Classes
 IModelBinder
 IValueProvider
 ModelMetadataProvider
 BindAttribute

 Validation
 Data Annotations
 IValidateObject


Action Results
 A controller action returns
something called an action result.
 Action results types:
 ViewResult  FileContentResult

 EmptyResult  FilePathResult

 RedirectResult  FileStreamResult

 JsonResult  HttpNotFoundResult

 JavaScriptResult  HttpRedirectResult

 ContentResult  HttpStatusCodeResult


Custom Action Result


ASP.NET MVC Filters
 Filters are custom classes that provide both a
declarative and programmatic means to add
pre-action and post-action behavior to
controller action methods.

[HandleError]
[Authorize]
public class CourseController : Controller
{
[OutputCache]
[RequireHttps]
public ActionResult Net( string name )
{
ViewBag.Course = BL.GetCourse(name);
return View();
}
}

Filter Interfaces

Action Method Action Result


Filter Order
 Filters run in the following order:
 Authorization filters

 Action filters

 Response filters

 Exception filters


Controller & Filters
 The Controller class implements each of the
filter interfaces.
 You can implement any of the filters for a
specific controller by overriding the
controller's On<Filter> method.
 OnAuthorization
 OnActionExecuting
 OnActionExecuted
 OnResultExecuting
 OnResultExecuted
 OnException


IAuthorizationFilter
 Make security decisions about whether to
execute an action method.
 AuthorizeAttribute

 RequireHttpsAttribute


IActionFilter Interface
 OnActionExecuting
 Runs before the action method.

 OnActionExecuted
 Runs after the action method


IResultFilter Interface
 OnResultExecuting
 Runs before the ActionResult object is executed.

 OnResultExecuted
 Runs after the result.
 Can perform additional processing of the result.
 The OutputCacheAttribute is one example of a result filter.


IExceptionFilter
 Execute if there is an unhandled exception
thrown during the execution of the ASP.NET
MVC pipeline.
 Can be used for logging or displaying an error page.

 HandleErrorAttribute is one example of an exception filter.


Handle Error Attribute
 You can specify an exception and the names
of a view and layout.
 Works only when custom errors
are enabled in the Web.config file
 <customErrors mode="On" /> inside
the <system.web>

 The view get
HandleErrorInfo


First Global Controller Action Last
Filter I Filter I Filter I Filter I Filter I
Filter II Filter II Filter II Filter II Filter II

Action Method Action Result

Authorization Action Result Exception
Filter I Filter I Filter I Filter I Filter I Filter II
Filter I Filter II
Filter I Filter II
Filter I Filter I Filter I Filter I Filter I Filter II
Filter I Filter II
Filter I Filter I Filter I Filter I
Filter II
Filter II Filter I Filter I Filter I Filter I
Filter II Filter I Filter I
Filter II Filter I
Filter II Filter I Filter I Filter I Filter I Filter I
Filter I

Action

Before After
Filter I Filter II
Filter I Filter II
Filter I Filter II
Filter I Filter II
Filter I Filter II
Filter II Filter I
Filter II Filter I
Filter II Filter I
Filter II Filter I
Filter II Filter I


Controller Context
1 6

2 3 4 5


Filters


Custom Filter
 You can create a filter in the following ways:
 Override one or more of the controller's On<Filter>
methods.

 Create an attribute class that derives from
ActionFilterAttribute or FilterAttribute.
 Register a filter with the filter provider
(the FilterProviders class).

 Register a global filter using the GlobalFilterCollection class.


Custom Filter


The Filter Provider Interface


Filter Providers
 By default, ASP.NET MVC registers the
following filter providers:
 Filters for global filters.

 FilterAttributeFilterProvider for filter attributes.

 ControllerInstanceFilterProvider for controller instances.

 The GetFilters method returns all of the
IFilterProvider instances in the service
locator.


Filter Summary
 Custom Filters
 IAuthorizationFilter
 IActionFilter
 IResultFilter
 IExceptionFilter

 IFilterProvider


View Extensibility


Creating a Custom View Engine


View Summary
 IViewEngine
 How to find the view?

 IView
 Render


MVC Internals & Extensibility Summary

Mvc
Routing RouteHandler
MvcHandler

Factory Activator

Action Name Method Authorization Model
Invoker Selector Selectror Filter Bind

Action Action Action Result View
Filer Method Filer Filter Engine

Result Exception
View
Filter Filter


Asp.net mvc internals & extensibility

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