Asp.Net Application_Start called again, after login

Question

Debugging my code in VS, I've seen that Global.asax´s Application_Start method is being called twice:

• First when the server starts
• Second after login

The login method does:

  AuthenticationCookie.SetSessionCookie(userName);
  FormsAuthentication.RedirectFromLoginPage(userName, false);
  System.Threading.Thread.CurrentPrincipal = user;

The Web.config file is as follows (excluding some 100% unrelated parts):

. . .

<appSettings>
    <add key="webpages:Version" value="2.0.0.0" />
    <add key="webpages:Enabled" value="false" />
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
</appSettings>
<!--
For a description of web.config changes for .NET 4.5 see http://go.microsoft.com/fwlink/?LinkId=235367.

The following attributes can be set on the <httpRuntime> tag.


  <system.net>
    <settings>
      <httpWebRequest useUnsafeHeaderParsing="true" />
    </settings>
  </system.net>

  <system.web>
    <compilation debug="true" targetFramework="4.5" />
        <authentication mode="Forms">
            <forms loginUrl="SignIn" protection="All" timeout="120" />
        </authentication>
        <pages controlRenderingCompatibilityVersion="4.0">
            <namespaces>
                <add namespace="System.Web.Helpers" />
                <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="System.Web.WebPages" />
            </namespaces>
        </pages>
        <!--
            If you are deploying to a cloud environment that has multiple web server instances,
            you should change session state mode from "InProc" to "Custom". In addition,
            change the connection string named "DefaultConnection" to connect to an instance
            of SQL Server (including SQL Azure and SQL  Compact) instead of to SQL Server Express.
      -->
        <sessionState mode="InProc" customProvider="DefaultSessionProvider" timeout="120">
            <providers>
                <add name="DefaultSessionProvider" type="System.Web.Providers.DefaultSessionStateProvider, System.Web.Providers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" connectionStringName="DefaultConnection" />
            </providers>
        </sessionState>
    </system.web>
    <system.webServer>
        <validation validateIntegratedModeConfiguration="false" />
        <modules runAllManagedModulesForAllRequests="true" />
        <handlers>
            <remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
            <remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
            <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
            <add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
            <add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
            <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
        </handlers>
    </system.webServer>