title: Compilation Error when change .Net framework from 4.5.2 to 4.5 in VS 2015 Community edition
body: <p>After changing my .Net framework from 4.5.2 to 4.5 in VS 2015 Community edition. I am getting following error. Did anyone know what is the issue and how to solve this. Look like compile version is different, but I have already modify my web.config to 4.5</p>
  
  <blockquote>
    <p>Server Error in '/' Application.</p>
    
    <p>Compilation Error    Description: An error occurred during the
    compilation of a resource required to service this request. Please
    review the following specific error details and modify your source
    code appropriately. </p>
    
    <p>Compiler Error Message: CS1617: Invalid option '6' for /langversion;
    must be ISO-1, ISO-2, 3, 4, 5 or Default</p>
    
    <p>Source Error:</p>
    
    <p>[No relevant source lines]</p>
    
    <p>Source File:    Line: 0 </p>
    
    <p>Show Detailed Compiler Output:</p>
    
    <p>C:\Program Files (x86)\IIS Express>
    "C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe" /t:library
    /utf8output /R:"C:\Users\admin\AppData\Local\Temp\Temporary ASP.NET
    Files\root\479d40ee\add72695\assembly\dl3\31bb6ea7\6a8168a8_dae8d001\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.dll"
    /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Configuration\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Configuration.dll"
    /R:"C:\WINDOWS...................</p>
    
    <p>Microsoft (R) Visual C# Compiler version 4.6.0079.0</p>
    
    <p>for C# 5 Copyright (C) Microsoft Corporation. All rights reserved.</p>
    
    <p>This compiler is provided as part of the Microsoft (R) .NET Framework,
    but only supports language versions up to C# 5, which is no longer the
    latest version. For compilers that support newer versions of the C#
    programming language, see
    <a href="http://go.microsoft.com/fwlink/?LinkID=533240" rel="noreferrer">http://go.microsoft.com/fwlink/?LinkID=533240</a></p>
    
    <p>error CS1617: Invalid option '6' for /langversion; must be ISO-1,
    ISO-2, 3, 4, 5 or Default</p>
  </blockquote>