Getting error in @model line after adding a namespace in view/webconfig

See more:

C#

ASP.NET

MVC4

ViewModel

Sir,

I add a .dll to a project and for using it in my view i add a namespace in web.Config(in view folder) but after adding namespace i am getting an error in all my .cshtml files in
@model line.

what is wrong..
my login.cshtml

@model myStore.Models.LoginModel
@using myStore
@using myStore.Models

@using mynamespace


i changed add this to add namespace in web.config.

<system.web.webPages.razor>
    <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=4.0.0.0, 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.Optimization"/>
        <add namespace="System.Web.Routing" />
         <add namespace="mynamespace" />
      </namespaces>
    </pages>
  </system.web.webPages.razor>

thanks in advance.