Routing Internals

Łukasz ŁysikASP.NET MVC 4 Study Group

Agenda

• Routes Registration• Routes Registration for Areas• How routing works?• Generating URLs• Debugging routes

ROUTES REGISTRATION

Routes Registration Overview

Are there any restrictions here?

Routes Registration Overview

Routes Registration MapRoute

RouteCollectionExtensions:

Routes Registration Route class

MySite/{controller}-{action}/{id}

Routes Registration Route class ParsedRoute

ParsedRoute

ContentPathSegment

LiteralSubsegment („MySite”)

SeparatorPathSegment ContentPathSegment

ParameterSubsegment {controller}

LiteralSubsegment „-”

ParameterSubsegment {action}

SeparatorPathSegment ContentPathSegment

ParameterSubsegments {id}

Routes Registration Route class Constraints

Routes Registration Route class Custom

Constraints

Problem: We want to have mechanism which closes our web site for maintenance for specified period of time.

Inputs:

Routes Registration Route class Custom

Constraints

Coding

Routes Registration Route class Custom

Constraints

Routes Registration Route class Custom

Constraints

Routes Registration Route class DataTokens

• Contain values associated with the route that are not used when ASP.NET routing determines whether a route matches a request.

• Custom data tokens can be defined and used by custom logic in route handler, controller, action, etc.

• Predefined DataTokens are related to Areas.

ROUTES REGISTRATION FOR AREAS

Routes Registration for Areas Overview

Routes Registration for Areas Overview

Problem: Multiple controllers with the same names

Routes Registration for Areas MapRoute

Routes Registration for Areas DataTokens collection

Area

Current area name.

Namespaces

Namespaces to search for controllers.

UseNamespaceFallback

Set to „false” to disable searching in other namespaces.

Q: In which part of request pipeline these two DataTokens are used?

A: In DefaultControllerFactory.

Routes Registration for Areas Usage of DataTokens

DefaultControllerFactory:

HOW ROUTING WORKS?

Route 1

URL 1

ParsedRoute 1

Defaults 1

Constraints 1

DataTokens 1

RouteHandler 1

Route 2

URL 2

ParsedRoute 2

Defaults 2

Constraints 2

DataTokens 2

RouteHandler 2

… Route n

URL n

ParsedRoute n

Defaults n

Constraints n

DataTokens n

RouteHandler n

How Routing Works? RouteTable.Routes

How Routing Works? Routing Process (1)

UrlRoutingModule RouteTable.RoutesDo you have any routes for this context?

Route 1 Route 2 Route n

. . .

ParsedRoute matches current URL?

Do I have any constraints?

Process constraints.Constraints satisfied?

Return null.Build and return RouteData.

No

NoNo

Yes

Yes

How Routing Works? Routing Process (2)

UrlRoutingModule RouteData(based on Route 2)

Give me IRouteHandler

IRouteHandlerGive me IHttpHandler

Tell IIS to use IHttpHandler which I

got from matched Route.

How Routing Works? RouteData

How Routing Works? Route.ProcessConstraint

How Routing Works? Route.GetRouteData

How Routing Works? Route.ProcessConstraint

URL GENERATION

URL Generation Overview

URL Generation Examples (1)

URL Generation Examples (2)

URL Generation Matching AlgorithmRouteCollection.GetVirtualPath(Supplied values)

Does Route have required parameters?

Did the call to GetVirtualPath specify a value for each required parameter?

Does Route have default values that do not correspond to URL parameter?

Does true value for that default, if specified, match the specified value?

Process constraints

Yes

Yes

Yes

NoRequired = with no default value

No match!No

No

URL: “todo/{action}”Defaults: controller=home action=index

No match!No

Yes

DEBUGGING ROUTES

• Possible problems:– Routes don’t work.– URL is routed to wrong controller/action.– DataTokens values are missing (are wrong).– Constraints don’t work.

• What we need?– Tool that will tell us which routes are being

matched, what RouteData parameters and DataTokens are.

Debugging Routes Problems

Debugging Routes How?

Q: How to write a tool that will debug routes?

Q: What is the name of static class which stores routes?

Q: Which request pipeline element uses RouteTable.Routes?

A: RouteTable.Routes

A: UrlRoutingModule

Demo

Debugging Routes Coding session

Debugging Routes Coding session

• RouteDebugger by Phil Haack:– http://

haacked.com/archive/2011/04/12/routedebugger-2.aspx

• How it works:– Registers own HTTP module.– Attach to Request_End event.– Writes route data at the bottom

of each view.

Debugging Routes RouteDebugger 2.0

References

Professional ASP.NET MVC 4(http://www.amazon.co.uk/Professional-ASP-NET-MVC-Wrox-Guides/dp/111834846X)

Questions?