I'm getting this exception:
System.Configuration.ConfigurationErrorsException: The value for the 'compilerVersion' attribute in the provider options must be 'v4.0' or later if you are compiling for version 4.0 or later of the .NET Framework.
What should I do to resolve this?
this should help
<configuration>
<!-- -->
<system.codedom>
<compilers>
<compiler language="c#;cs;csharp" extension=".cs" warningLevel="4"
type="Microsoft.CSharp.CSharpCodeProvider,System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<providerOption name="CompilerVersion" value="v4.0"/>
<providerOption name="WarnAsError" value="false"/>
</compiler>
</compilers>
</system.codedom>
<!-- -->
</configuration>
We had accidentally copy-pasted Web.config into C:\inetpub\wwwroot. This accidentally copy-pasted Web.config had mismatching configuration and caused the compilerVersion error for us. Deleting the Web.config solved the problem for us.
In my case, I am using an old Webform website (V 2.0), need to append a new application which is developed in MVC4.0. This same error I was facing and after many permutations and combination of the given solution, I wrapped the whole web.comfig of the parent application in the following tag
<location path="." inheritInChildApplications="false">
...... web config tags here........
</location>