title: Visual Studio 2015 fail to load package because Microsoft.VisualStudio.Shell.15.0 fail to load
body: <p>I've built a Visual Studio extension for Visual Studio 2015 and 2017. I've developed it with 2017 and everything works great on 2017.</p>
  
  <p>When I install it on VS 2015 I get an error message saying it failed to load my package. In the visual studio <code>ActivityLog.xml</code> file I see the following error.</p>
  
  <p>How can I enable both VS 2015 and 2017 to run the extension?</p>
  
  <pre><code>CreateInstance failed for package [MainWindowPackage]
  Source: 'mscorlib' 
  Description: Could not load file or assembly 'Microsoft.VisualStudio.Shell.15.0, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified. 
  
  System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.VisualStudio.Shell.15.0, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified. 
  
  File name: 'Microsoft.VisualStudio.Shell.15.0, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' at System.Reflection.RuntimeAssembly.GetType(RuntimeAssembly assembly, String name, Boolean throwOnError, Boolean ignoreCase, ObjectHandleOnStack type) at System.Reflection.RuntimeAssembly.GetType(String name, Boolean throwOnError, Boolean ignoreCase) at System.Activator.CreateInstanceFromInternal(String assemblyFile, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence securityInfo) at System.AppDomain.CreateInstanceFrom(String assemblyFile, String typeName) 
  </code></pre>