visual studio 2015 IIS Express cannot debug asp.net 4 project

Question

I was working on 2 projects using VS 2013. Recently I had to switch to VS 2015 and opened these projects in the same. One of the 2 project, which is a .net 4.5 framework version project works fine, and I am able to debug in IIS Express. However, the second project - .net 4.0 project - I cannot debug using IIS express. When I try to debug I get a 500 error

The configuration section 'system.web.extensions' cannot be read because it is missing a section declaration

I managed to resolve that particular error with help from this stackoverflow link The configuration section 'system.web.extensions' cannot be read because it is missing a section declaration

But still I could not debug as I got another error

Unrecognized attribute 'targetFramework' at this line : in web.config

I am not able find a solution to this problem. there are some articles which suggest solutions for IIS, but not for IIS Express. I am not able to understand why this happens, as the other project (.net 4.5) works fine, so this is not a problem with IIS express framework config, but project related. I did not make any changes to code whiles moving from vs 2013 to vs 2015. What can I do to debug the code using IIS express in vs2015. preferably by not making changes to web.config as this is working fine on the production server.

Answer 1

First, you remove the targetFramework from the trouble line in the web.config`

IIS Express configuration is stored in an XML file for each solution. In that file, you can find <applicationPools> section and set their managedRuntimeVersion attribute.

This file is located in your "$(SolutionFolder)\.vs\applicationhost.config". Note that the ".vs" folder is hidden by default. The file structure is similar to this:

<configuration>
.
.
.

<system.applicationHost>

    <applicationPools>
        <add name="Clr4IntegratedAppPool" managedRuntimeVersion="v4.0" managedPipelineMode="Integrated" CLRConfigFile="%IIS_USER_HOME%\config\aspnet.config" autoStart="true" />
        <add name="Clr4ClassicAppPool" managedRuntimeVersion="v4.0" managedPipelineMode="Classic" CLRConfigFile="%IIS_USER_HOME%\config\aspnet.config" autoStart="true" />
        <add name="Clr2IntegratedAppPool" managedRuntimeVersion="v2.0" managedPipelineMode="Integrated" CLRConfigFile="%IIS_USER_HOME%\config\aspnet.config" autoStart="true" />
        <add name="Clr2ClassicAppPool" managedRuntimeVersion="v2.0" managedPipelineMode="Classic" CLRConfigFile="%IIS_USER_HOME%\config\aspnet.config" autoStart="true" />
        <add name="UnmanagedClassicAppPool" managedRuntimeVersion="" managedPipelineMode="Classic" autoStart="true" />
        <applicationPoolDefaults managedRuntimeLoader="v4.0">
            <processModel />
        </applicationPoolDefaults>
    </applicationPools>

   <sites>
        <site name="WebSite1" id="1" serverAutoStart="true">
            <application path="/" applicationPool="Clr4IntegratedAppPool">
                <virtualDirectory path="/" physicalPath="%IIS_SITES_HOME%\WebSite1" />
            </application>
            <bindings>
                <binding protocol="http" bindingInformation=":8080:localhost" />
            </bindings>
        </site>

.
.
.
</configuration>

Answer 2

Open your IIS and change your Application pool setting.

Select the right .NET Framework version as the image shown below: