OWIN Startup Class Missing

Question

I m getting this error as my project is not able to find the reference for OWIN startup class  I ve even installed all the OWIN reference packages through Nuget still getting the same issue  I m using Visual Studio 2012 and MVC4    The following errors occurred while attempting to load the app         No assembly found containing an OwinStartupAttribute    No assembly found containing a Startup or  AssemblyName  Startup class  To disable OWIN startup discovery  add the appSetting   owin AutomaticAppStartup with a value of  false  in your web config    To specify the OWIN startup Assembly  Class  or Method  add the   appSetting owin AppStartup with the fully qualified startup class or   configuration method name in your web config

User · Answer

While I can t fully explain why this solved the issue for me  I ran into a problem like this after I changed my API project to build to separate  debug and  release folders  Once I reverted that change back to build to a single  bin folder things started working    I wrote up my experience here  Can  39 t get the OWIN Startup class to run in IIS Express after renaming ASP NET project file

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I had this problem when I got the latest on TFS while other projects were open in multiple instances of VS  I already have all the fixes above  Reopening VS fixed the problem

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In my case I logged into ftp server  Took backup of current files on ftp server  Delete all files manually from ftp server  Clean solution  redeployed the code  It worked

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Have a look for the Startup cs file  you might be missing one of these   This file is the entry point for OWIN  so it sounds like this is missing   Take a look at OWIN Startup class here to understand whats going on   As your error specifies  you can disable this in the web config by doing the following        To disable OWIN startup discovery  add the appSetting   owin AutomaticAppStartup with a value of  false  in your web config

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This could be faced in Visual Studio 2015 as well when you use the Azure AD with a MVC project  Here it create the startup file as Startup Auth cs in App Start folder but it will be missing the    assembly  OwinStartup typeof MyWebApp Startup      So add it and you should be good to go  This goes before the namespace start

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I tried most of the recommended fixes here  and still couldn t avoid the error message  I finally performed a combination of a few recommended solutions   Added this entry to the top of the AppSettings section of my web config   lt add key  quot owin AutomaticAppStartup quot  value  quot false quot   gt   Expanded the References node of my project and deleted everything that contained the string OWIN   I felt safe doing so since my organization is not  and won t be  an active OWIN provider in the future    I then clicked Run and my homepage loaded right up

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It is also possible to get this exception  even when you have a correctly configured startup class  if running through IIS Express and your virtual directory is not configured correctly   When I encountered this issue  the resolution was simply to press the  Create Virtual Directory  button in the  Web  tab of project properties  Using Visual Studio 2013

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I ran into this problem after experimenting with SignalR and then removing it from the project  To resolve I had to delete the contents of the bin folder for the site on the remote server and then publish again

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I had this problem  understand this isn t what was wrong in the OP s case  but in my case I did have a Startup class  it just wasn t finding it by default   My problem was the I had spaces in my Assembly Name  and hence the default namespace was different from assembly name  hence the namespace for the startup class was different than the assembly name   As the error suggests  by convention it looks for  Assembly Name  Startup for the class    so be sure the namespace for your Startup class is the same as the Assembly name  Fixed the problem for me

User · Answer

Just check that your packages config file is checked in  when excluded  there will be a red no-entry symbol shown in the explorer   For some bizarre reason mine was excluded and caused this issue

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In our project  we didn t need the OWIN functionality  so we removed all the owin references from the initial ASP NET MVC template project  The problem occured after removing the OWIN startup class   The problem was the extra owin dll s in my bin folder  When I deleted them  the problem was resolved  You should delete them by deleting the bin folder  Clean Solution does not delete these dlls   Somehow  IIS still executes the OWIN dll s when they are in the bin folder

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If you don t want to use the OWIN startup  this is what you should add to your web config file   Under AppSettings add the following line        lt add key  owin AutomaticAppStartup  value  false    gt    This is how it should look like in your web config      lt appSettings gt       lt add key  owin AutomaticAppStartup  value  false    gt     lt  appSettings gt

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I kept getting the same error when I started my project using the Browser Link Dashboard in VS2013  But  when I ran my project in debug mode  it would work  I could not figure out why and how to get the Browser Link Dashboard working  I checked the startup file  it was fine  added the appSetting line  as described in some of the answers     but nothing worked    Apparently  what I was doing wrong was clicking on the WRONG link in the Browser Dashboard  All the Solutions projects links show in the Browser Dashboard  but only the startup projects link works  You need to click on the link of the startup project    Example  I have 2 projects  both show in the Browser Dashboard  but only the one marked as the start up project will work  shows as bold in the Solution Explorer   I thought this may help someone do the obvious  it cost me 2 days to stumble on to the obvious

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In my case  I had renamed the project and changed it s folder structure  I found that updating the RootNameSpace and AssemblyName in the  csproj file where the error was being thrown resolved the error  If you have modified paths of your project I d recommend checking this as well    lt RootNamespace gt Company Product WebAPI lt  RootNamespace gt   lt AssemblyName gt Company Product WebAPI lt  AssemblyName gt

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On Visual Studio 2013 RC2  there is a template for this  Just add it to App Start folder     The template produces such a class   using System  using System Threading Tasks  using Microsoft Owin  using Owin    assembly  OwinStartup typeof WebApiOsp App Start Startup     namespace WebApiOsp App Start       public class Startup               public void Configuration IAppBuilder app                           For more information on how to configure your application  visit http   go microsoft com fwlink  LinkID 316888

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First you have to create your startup file and after you must specify the locale of this file in web config  inside appSettings tag with this line    lt add key  owin AppStartup  value   NameSpace  Startup   gt   It solved my problem

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Create One Class With Name Startup this will help you     public class Startup      public void Configuration IAppBuilder app             app MapSignalR

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My case  I had startup file  but it is excluded in the project  I just included it and the error left

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Are you really trying to add OWIN to your project or is this something unexpected     In case you want to add OWIN  adding a Startup class is the way to go  In case you don t need any reference to Owin   delete Owin dll from your  bin folder    Owin dll is the one trying to identify the Startup class

[c#] OWIN Startup Class Missing

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