OwinStartup not firing

Question

I had the OwinStartup configuration code working perfectly and then it stopped working. Unfortunately I'm not sure exactly what I did to get it to stop working and am having a really hard time figuring it out.

To make sure I have the basics covered, I doubled checked to make sure the I have the

[assembly:OwinStartup(typeof(WebApplication.Startup))] 

attribute assigned properly and made sure that I don't have an appSetting for owin:AutomaticAppStartup that is set to false so I made one set to true to be safe as there was nothing there before.

<add key="owin:AutomaticAppStartup" value="true" />

I also tried specifically calling out the appSetting:

<add key="owin:appStartup" value="WebApplication.Startup" />

Before it stopped working I upgraded the Microsoft.Owin.Security NuGet packages to 2.0.2, so I tried reverting them to 2.0.1 (that was a pain) but it didn't change anything. I have WebActivator installed on the project and am using that to bootstrap other things but I've tested that on a fresh WebApplication template and it works there so I don't think that is the culprit.

I also tried removing my Startup class and using Visual Studio to add a new one using the OWIN Startup Class type in Add New Item and that isn't getting called either. Next I tried adding a second Startup class since I know it will throw an exception if there is more than one OwinStartup attributes defined, but it isn't throwing any exception there.

Not sure what else to try. Any thoughts?

Update

Turns out that Resharper removed the reference to Microsoft.Owin.Host.SystemWeb when I used it to remove unused references.

Answer 1

Make sure you have installed Microsoft.Owin.Host.SystemWeb package in the project. This package is needed for startup detection in IIS hosted applications. For more information you can refer to this article.

Answer 2

If you've upgraded from an older MVC version make sure you don't have

  <add key="owin:AutomaticAppStartup" value="false" />

in your web.config. It will suppress calling the startup logic.

Instead change it to true

  <add key="owin:AutomaticAppStartup" value="true" />

I realize you already mentioned this but sometimes people (like me) don't read the whole question and just jump to the answers...

Somewhere along the line - when I upgraded to MVC 5 this got added and I never saw it until today.

Answer 3

Alternative answer to the original problem discussed - Owin "not firing." In my case I spent hours thinking it wasn't firing due to being unable to set a breakpoint in it.

When debugging OWIN startup in visual studio

• IIS Express - Running "F5" will break on the OWIN startup code

• IIS - Running "F5" will not break until after OWIN (and global.asax) code is loaded. If you attach to W3P.exe you will be able to step into it.

Answer 4

If you are having trouble debugging the code in the Startup class, I have also had this problem - or I thought I did. The code was firing but I believe it happens before the debugger has attached so you cannot set breakpoints on the code and see what is happening.

You can prove this by throwing an exception in the Configuration method of the Startup class.