If you get a

An unhandled exception has occurred while executing the request. 
System.BadImageFormatException: Index not found. (Exception from HRESULT: 0x80131124) 

error when publishing your website through Visual Studio, a couple of things to check are:

• When publishing the application to Azure make sure that the “Remove Additional Files at destination” option is checked.
  
  
• Made sure that all the projects(only one) were being build as “Any CPU” in both “debug” and “release” configuration.