System.BadImageFormatException An attempt was made to load a program with an incorrect format

Question

I\'m writing a plug-in for another program that is based on a public .NET API. Typically these plugins are made by creating a class library DLL that references the API assem

Answer 1

I was having problems with a new install of VS with an x64 project - for Visual Studio 2013, Visual Studio 2015 and Visual Studio 2017:

Tools
  -> Options
   -> Projects and Solutions
    -> Web Projects
     -> Check "Use the 64 bit version of IIS Express for web sites and projects"