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Hi Team

I am facing this systemnull exception on my Identityconfig.cs and how do i fix this issue?

What I have tried:

public class ApplicationSignInManager : SignInManager<ApplicationUser, string>
       public ApplicationSignInManager(ApplicationUserManager userManager, IAuthenticationManager authenticationManager)
           : base(userManager, authenticationManager) //Systemexception as null here.

       public override Task<ClaimsIdentity> CreateUserIdentityAsync(ApplicationUser user)
           return user.GenerateUserIdentityAsync((ApplicationUserManager)UserManager);

       public static ApplicationSignInManager Create(IdentityFactoryOptions<ApplicationSignInManager> options, IOwinContext context)
           return new ApplicationSignInManager(context.GetUserManager<ApplicationUserManager>(), context.Authentication);
Updated 3-Mar-20 3:18am

1 solution

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!
Share this answer
gcogco10 3-Mar-20 8:22am    
userManager is empty
OriginalGriff 3-Mar-20 8:30am     CRLF
So you need to find out why - so trace back through your code and find out where it is actually assigned, and to what. It's a parameter, so look at where it's called. Look at what that uses, and follow on back until you find out why. We can't do any of that for you - we don't have your code, data, and system running in front of us!
Dave Kreskowiak 3-Mar-20 8:48am     CRLF
That means you didn't pass in an ApplicationUserManager object to the constructor of this class to create an instance of it. Sorry, YOU are the only one who can track that down. Where did you try to create an instance of ApplicationSignInManager, and why didn't you provide the objects it's looking for?
gcogco10 3-Mar-20 9:03am    
ApplicationSignInManager its on IdentityConfig.cs, ManagerController and AccountController

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