MSSQL Webadmin shows error: Compiler Error Message: Name 'AppInterface' is not declared.
This error is due to the misconfiguration of sqladmin site in the IIS . Subfolder mssql of the site should be an application.
1. Open the server manager
2. Under the Roles select IIS manager
3. Expand the domains and select mssql folder under the sqladmin site
4. Right click on the folder mssql and select "Convert to application".
