ASP.NET Core MVC interview questions covering advanced routing, filters, areas & application structure.
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Advanced routing goes beyond the basic {controller}/{action}/{id?} pattern and uses route constraints, named routes, route order, attribute templates, areas, parameter transformers, and custom routing conventions to create precise URL structures.
Route constraints restrict which values can match a route parameter. Common constraints include int, guid, bool, datetime, length, min, max, and regex-based constraints.
An optional route parameter uses ? to indicate that the URL segment may be absent. A default route value supplies a value when a route segment is not present.
A named route gives a route a stable identifier that can be used for URL generation or redirects. This is useful when code should target a particular route definition rather than depend on controller/action discovery.
Attribute routing supports replacement tokens such as [controller], [action], and [area]. At application startup, MVC replaces these tokens with values derived from the controller, action, or area.
A route parameter transformer can change how route values are represented during URL generation. A common example is converting PascalCase controller or action names into kebab-case URLs.
When multiple endpoints could match a request, routing uses endpoint precedence, order, constraints, and other metadata to select the best candidate. More specific route patterns generally take precedence over broader patterns.
URL generation creates a URL from route values instead of hard-coding a path. MVC helpers such as Url.Action, RedirectToAction, anchor Tag Helpers, and LinkGenerator use the configured endpoints to generate URLs.
LinkGenerator is a routing service that can generate paths or absolute URIs outside of Razor Tag Helpers and controller convenience methods. It is useful in services that need to generate application links, such as notification or email workflows.
Areas divide a large MVC application into functional sections, each with its own controllers, views, and routing. Common examples include Admin, Customer, Staff, or Management sections.
An area commonly contains its own Controllers, Views, and optionally Models or other feature-specific folders beneath Areas/{AreaName}. Views normally follow the same controller-based convention inside the area's Views folder.
A conventional area route includes an {area:exists} segment and is normally mapped before the application's general default route. Attribute routing can also include [area] or explicit area templates.
Use the asp-area Tag Helper together with asp-controller and asp-action. This ensures that URL generation includes the intended area route value.
No. Areas are an organizational and routing feature, not a security boundary. An Admin area is not protected merely because its URL begins with /Admin.
MVC filters are components that run at defined stages around MVC action execution. They support cross-cutting concerns that are specific to MVC, such as authorization, resource handling, action execution, exception handling, and result processing.
The main MVC filter categories are authorization filters, resource filters, action filters, exception filters, and result filters. They execute at different points in the MVC pipeline and therefore solve different problems.
An authorization filter runs early in the MVC filter pipeline and determines whether the current request is authorized to continue. In most applications, authorization should be expressed through ASP.NET Core authorization policies and the Authorize attribute rather than custom authorization-filter logic.
An action filter runs immediately before and/or after an MVC action method executes. It can inspect action arguments, ModelState, controller information, and the resulting action result.
A resource filter runs after authorization and surrounds much of the remaining MVC pipeline. Because it executes before model binding, it can be useful for concerns such as caching or short-circuiting expensive MVC processing.
An exception filter can observe or handle unhandled exceptions that occur during parts of MVC action processing. It can convert an exception into an MVC result by marking the exception as handled.
A result filter runs before and after execution of an MVC action result. It can inspect or modify result processing for supported result types.
MVC provides synchronous filter interfaces such as IActionFilter and asynchronous equivalents such as IAsyncActionFilter. An asynchronous filter should be used when its work requires asynchronous I/O.
Global filters are added to MVC options and apply broadly to MVC requests. Attribute-based filters can be placed on a controller to affect all of its actions or on a specific action for narrower scope.
ServiceFilter resolves the filter itself from dependency injection, so the filter type must be registered as a service. TypeFilter can create the specified filter type using ObjectFactory while resolving its constructor dependencies from DI; the filter type itself does not have to be registered in the same way.
Keep public routes predictable and unambiguous, use constraints when they improve endpoint selection, and generate URLs through routing rather than hard-coding paths. Use Areas to organize genuinely large functional sections, but apply explicit authorization because an area is not a security boundary.