MVC 4 website load shows HTTP Error 500.19 - web-config

Question

I created a new ASP.NET MVC 4 application based on Internet application template, I could succesfully run it and authenticate user from within VS 2012 Express.
Then published it to a folder in wwwroot, then in IIS 7.5 manager created a virtual directory pointing to that folder, and converted it to an application using a separate 4.0 integrated pool.
When I tried to browse the application from within the IIS manager I get the next error:
HTTP Error 500.19 - Internal Server Error,
The requested page cannot be accessed because the related configuration data for the page is invalid.
Config Error: Cannot add duplicate collection entry of type 'add' with unique key attribute 'name' set to 'ExtensionlessUrlHandler-Integrated-4.0'
Config source:
56: <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"/>
57: <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" resourceType="Unspecified" requireAccess="Script" preCondition="integratedMode,runtimeVersionv4.0" />
58: </handlers>
searched here,I found the corresponding answer:
Resolution 1
Delete the malformed XML element from the ApplicationHost.config file or from the Web.config file.
My web.config file is as below:
<?xml version="1.0"?>
<configuration>
<configSections>
<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false"/>
</configSections>
<connectionStrings>
<add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=aspnet-digixMVC4-20120915233326;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\aspnet-digixMVC4-20120915233326.mdf" providerName="System.Data.SqlClient"/>
</connectionStrings>
<appSettings>
<add key="webpages:Version" value="2.0.0.0"/>
<add key="webpages:Enabled" value="false"/>
<add key="PreserveLoginUrl" value="true"/>
<add key="ClientValidationEnabled" value="true"/>
<add key="UnobtrusiveJavaScriptEnabled" value="true"/>
</appSettings>
<!--
The following attributes can be set on the <httpRuntime> tag.
<system.Web>
<httpRuntime targetFramework="4.5"/>
</system.Web>
-->
<system.web>
<compilation targetFramework="4.5"/>
<httpRuntime/>
<authentication mode="Forms">
<forms loginUrl="~/Account/Login" timeout="2880"/>
</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>
</system.web>
<system.webServer>
<validation validateIntegratedModeConfiguration="false"/>
<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"/>
<add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" resourceType="Unspecified" requireAccess="Script" preCondition="integratedMode,runtimeVersionv4.0" />
</handlers>
</system.webServer>
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364g85"/>
<bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0"/>
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364g85"/>
<bindingRedirect oldVersion="1.0.0.0-4.0.0.0" newVersion="4.0.0.0"/>
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364g85"/>
<bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0"/>
</dependentAssembly>
</assemblyBinding>
</runtime>
<entityFramework>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework"/>
</entityFramework>
</configuration>
As I am a poorly skilled developer in MVC 4, I would ask if someone could find out the malformed xml element in the file above.

Answer 1

This is true for ASP.NET WebAPI 5.2 too..
I had
<add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
<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" />
Which I changed to
<add name="ExtensionlessUrlHandler-Integrated-4.0a" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
<add name="ExtensionlessUrlHandler-Integrated-4.0b" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
Thats it.. It worked.

Answer 2

you have the same name in twice. the name must be unique.
current config
<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"/>
<add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" resourceType="Unspecified" requireAccess="Script" preCondition="integratedMode,runtimeVersionv4.0" />
change to
<add name="ExtensionlessUrlHandler-Integrated-4.0a" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0"/>
<add name="ExtensionlessUrlHandler-Integrated-4.0b" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" resourceType="Unspecified" requireAccess="Script" preCondition="integratedMode,runtimeVersionv4.0" />

Answer 3

I experienced a similar problem to this.
what worked for me was to remove, then re-add the handler:
My guess is that if by default this is enabled in the IIS Server already, it may trigger this error.
I am using IIS 10, MVC 5, .NET Framework 4.6.1
Hope this helps :-)