Description

When updating an On-Premise TEOS Server from 3.x.x to 3.3.0 the installer runs different process. One of these is updating the “Web.config” file. There is a chance that this can go wrong. This guide will explain how to fix the compile error CS8401 on TEOS Manage 3.3.0.

Please do not use this guide for any lower version then TEOS Manage 3.3.0, this could corrupt the system.

Requirements

• Admin access to TEOS web server

How to fix compile CS8401 error “please use language version '8.0' or greater”

1. Login to the TEOS Server.  
    
2. Open explorer and search for “Program files/TEOS Manage/www/backbone”. Depending on system configuration the “C:/” could be different, search accordingly.
   
    
3. In this folder there should be a file called “Web.config”, we first need to make a backup of this file.
   
    
4. Copy the file and put it in a different location for example “Desktop”. 
   
    
5. Once a backup of the file has been made, we can edit the one in “Program files/TEOS Manage/www/backbone”, right click the “Web.config” file and select edit.
   
    
6. Do CTRL + F to open the “Find” menu.
   
    
7. We need to search for “langversion: “, select “Find Next”. This will bring you down the page in the tags “Compilers”. It could be that this looks different in your case, this is fine.
   
    
8. We need to replace the bit what starts and ends with <compilers>.
   
    

9. Replace it with the exact following code:

       <compilers>
   <compiler language="c#;cs;csharp" extension=".cs" warningLevel="4" compilerOptions="/langversion:default /nowarn:1659;1699;1701;612;618"
   type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
   <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" warningLevel="4"
   compilerOptions="/langversion:default /nowarn:41008,40000,40008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+"
   type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
   </compilers>

   
    

10. It should look exactly like this:
    
     
11. After replacing the code select “File” in the top left corner and click “Save”.
    
     
12. Reload and re-log into the TEOS Manage web environment to see that the problem has been solved. 

If the problem still persists, please make contact with support. 
support@teos.support