System Web MVC WebViewPage is not allowed - asp.net-mvc

Question

I having this error but I cant find the way to help it
Server Error in '/' Application.
Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.
Parser Error Message: 'System.Web.Mvc.WebViewPage' is not allowed here because it does not extend class 'System.Web.UI.Page'.
Source Error:
<add name="ApplicationInsightsWebTracking"
type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule,
Microsoft.AI.Web" />
</httpModules>
**<pages pageBaseType="System.Web.Mvc.WebViewPage">**
<namespaces>
<add namespace="GridMvc" />
Source File: C:\app\web.config Line: 32

Answer 1

It is clear that System.Web.Mvc.WebViewPage namespace added at the wrong place (as shown by httpModules used before the line causing problem). The correct place to add respective namespace is in a web.config file inside Views folder under system.web.webPages.razor element, as shown below:
<system.web.webPages.razor>
<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
<pages pageBaseType="System.Web.Mvc.WebViewPage">
<namespaces>
<add namespace="System.Web.Mvc" />
<add namespace="System.Web.Mvc.Ajax" />
<add namespace="System.Web.Mvc.Html" />
<add namespace="System.Web.Routing" />
<add namespace="GridMvc" />
<!-- other namespaces -->
</namespaces>
</pages>
</system.web.webPages.razor>
The pages element under system.web is primarily intended for webforms project configuration (under System.Web.UI.Page namespace), which often contains 2 attributes (validateRequest & clientIDMode):
<pages validateRequest="true" clientIDMode="AutoID">
To use MVC version of pageBaseType attribute, you need to check if current pages element exists inside system.web.webPages.razor. In this case you added the namespace incorrectly under system.web, which doesn't inherit System.Web.Mvc namespace & throwing disallowed namespace error.