Default document is not working due to bad web.config settings

Question

I am working on a legacy application deployed on IIS 8.5 and it should display default.aspx page automatically but its not and displays 404 error. To test, I added a new website on same machine and uploaded an empty default.aspx page and this works. When I paste web.config again in new website, same error 404 again.

I tried manually adding default pages in web.config itself, but again same issue.

So this looks like a miss-configuration in web.config file, can you please look into below web.config, let me know if you see any issue.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <sectionGroup name="elmah">
      <section name="security" requirePermission="false" type="Elmah.SecuritySectionHandler, Elmah" />
      <section name="errorLog" requirePermission="false" type="Elmah.ErrorLogSectionHandler, Elmah" />
      <section name="errorMail" requirePermission="false" type="Elmah.ErrorMailSectionHandler, Elmah" />
      <section name="errorFilter" requirePermission="false" type="Elmah.ErrorFilterSectionHandler, Elmah" />
    </sectionGroup>
  </configSections>
  <system.web>
    <pages enableViewStateMac="false" controlRenderingCompatibilityVersion="4.0" />
    <httpRuntime maxRequestLength="2097151" executionTimeout="360" />
    <httpHandlers>
      <add verb="*" path="Test_*.aspx" type="Test.Web.Domain.Abstract.UrlRewriter" validate="false" />
    </httpHandlers>
    <compilation debug="true" targetFramework="4.5">
      <assemblies>
        <add assembly="System.Web.Extensions.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />
        <add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
      </assemblies>
    </compilation>
    <httpModules>
      <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" />
      <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" />
      <add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah" />
    </httpModules>
    <customErrors mode="RemoteOnly" defaultRedirect="~/500.aspx">
      <error statusCode="404" redirect="~/404.aspx" />
      <error statusCode="500" redirect="~/500.aspx" />
    </customErrors>
  </system.web>
  <system.webServer>
    <httpErrors errorMode="Detailed" />
    <asp scriptErrorSentToBrowser="true" />
    <directoryBrowse enabled="true" />
    <validation validateIntegratedModeConfiguration="false" />
    <modules>
      <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" preCondition="managedHandler" />
      <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" preCondition="managedHandler" />
      <add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah" preCondition="managedHandler" />
    </modules>
  </system.webServer>
  <system.webServer>
    <handlers>
      <remove name="ScriptResource" />
      <add name="*.aspx_*" path="Test_*.aspx" verb="*" type="Events.WebFormHandlerFactory" />
      <add name="HTMLHandler" path="*.aspx" verb="GET,HEAD,POST,DEBUG" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="Script" preCondition="integratedMode,runtimeVersionv4.5,bitness32" type="System.Web.UI.PageHandlerFactory" />
    </handlers>
  </system.webServer>
  <system.webServer>
    <staticContent>
      <remove fileExtension=".woff" />
      <mimeMap fileExtension=".woff" mimeType="application/x-font-woff" />
      <remove fileExtension=".ttf" />
      <mimeMap fileExtension=".ttf" mimeType="application/octet-stream" />
      <remove fileExtension=".svg" />
      <mimeMap fileExtension=".svg" mimeType="image/svg+xml" />
      <remove fileExtension=".mp4" />
      <mimeMap fileExtension=".mp4" mimeType="video/mp4" />
    </staticContent>
  </system.webServer>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Data.Edm" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.6.4.0" newVersion="5.6.4.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Data.Services.Client" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.6.4.0" newVersion="5.6.4.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Data.OData" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.6.4.0" newVersion="5.6.4.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-7.0.0.0" newVersion="7.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.WindowsAzure.MediaServices.Client" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.3.0.0" newVersion="3.3.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.WindowsAzure.MediaServices.Client.Common.BlobTransfer" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.3.0.0" newVersion="3.3.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Net.Http.Primitives" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-4.2.29.0" newVersion="4.2.29.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
  <elmah>
    <security allowRemoteAccess="true" />
    <errorLog type="Elmah.SqlErrorLog, Elmah" connectionStringName="SqlCon" />
  </elmah>
  <location path="AAAAA.aspx">
    <system.web>
      <pages validateRequest="false" />
      <httpRuntime requestValidationMode="2.0" />
    </system.web>
  </location>
</configuration>

In the above code, I doubt on line

    <handlers>
      <remove name="ScriptResource" />
      <add name="*.aspx_*" path="Test_*.aspx" verb="*" type="Events.WebFormHandlerFactory" />
      <add name="HTMLHandler" path="*.aspx" verb="GET,HEAD,POST,DEBUG" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="Script" preCondition="integratedMode,runtimeVersionv4.5,bitness32" type="System.Web.UI.PageHandlerFactory" />
    </handlers>

Its runtimeVersion is 4.5 which is also target framework but scriptProcessor has v4.0.30319 this smells like a bug.

Any input is highly appreciated.

Answer 1

There was no any issue in web.config, this issue appeared only after I enabled MVC bits in existing web form application.

MVC application overrides existing web form extension based URL so when request has no extension (.aspx) this maps request to default route i.e. domain.com/Home/Index which is not available in my application hence I see 404 Not Found.

Now in order to setup or prevent this MVC defaults, we can use

routes.IgnoreRoute("");

Here the code which works like charm.

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    routes.IgnoreRoute("");

    routes.MapRoute(
        name: "Default",
        url: "{controller}/{action}/{id}",
        defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
    );
}

Hope this will save your time.

Answer 2

Can you try with only one system.webServer entry.