Why does .NET generate two web.config files in an MVC asp.net application?

asp.net-mvc asp.net-mvc-3 web-config
Datta picture Datta · May 7, 2014 · Viewed 30.4k times · Source

I am new in MVC 3. What is the reason to use two web.config files?

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What is difference between that 2 web.config files, and what is the purpose of each and its function?

Answer

StuartLC picture StuartLC · May 7, 2014

This is an example of web.config file inheritance. From MSDN

You can distribute ASP.NET configuration files throughout your application directories to configure ASP.NET applications in an inheritance hierarchy. This structure allows you to achieve the level of configuration detail that your applications require at the appropriate directory levels without affecting configuration settings at higher directory levels.

Specifically, for MVC projects, the web.config in the View subdirectory is used to tailor the .cshtml / .aspx files. You can use web.config files in subfolders to extend, override, and remove settings inherited from the app's own root, and further up the hierarchy, e.g. up to machine.config

Common configurations in the /Views/web.config include:

  • Blocking requests attempting to access razor and aspx views directly (these need to be served from Controllers via the appropriate routes). A 404 response is configured for such direct requests, e.g.

<add path="*" verb="*" type="System.Web.HttpNotFoundHandler"/>
  • To setup default import namespaces for the view pages, which would otherwise have to be explicitly added via using. You can add namespaces for your common custom assemblies here (e.g. custom html helper extensions) e.g.

  <namespaces>
    <add namespace="System.Web.Mvc" />
    <add namespace="System.Web.Mvc.Ajax" />
    <add namespace="System.Web.Mvc.Html" />
    ...
  • To configure the anti-xss RequestValidation filter for MVC. The comment added in the config explains this best:

<!--
    Enabling request validation in view pages would cause validation to occur
    after the input has already been processed by the controller. By default
    MVC performs request validation before a controller processes the input.
    To change this behavior apply the ValidateInputAttribute to a
    controller or action.
 -->

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