Value cannot be null error when using GenerateEmailConfirmationTokenAsync?

Question

I am using the following command:

var code = await _userManager.GenerateEmailConfirmationTokenAsync(user);

And I get the following error with stack trace:

    System.ArgumentNullException: Value cannot be null.
Parameter name: value
   at System.IO.BinaryWriter.Write(String value)
   at Microsoft.AspNetCore.Identity.DataProtectorTokenProvider`1.GenerateAsync(String purpose, UserManager`1 manager, TUser user)
   at n8rpg.Controllers.AccountController.Register(RegisterViewModel model) in D:\Source\n8rpg\n8rpg\n8rpg\Controllers\AccountController.cs:line 62
   at Microsoft.AspNetCore.Mvc.Internal.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeActionMethodAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeNextActionFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeInnerFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
   at Microsoft.AspNetCore.Builder.RouterMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.MigrationsEndPointMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

I tried manually putting values in all the user properties. I can't figure out how to debug the thing to find out where my null value is... Any tips?

Answer 1

this is GenerateAsync method of DataProtectorTokenProvider class the point that throws is showed in picture :

the point that throws is showed in picture

in my case i defined Id property in my User class :

   public class ApplicationUser : IdentityUser<long>,IFormModel,IEntity
{
    
    public long Id { get; set; }
....

also you can check this answer

Answer 2

Most likely "Id" property of the "user" instance is null. You need to CreateUser first. When it's created successfully, you can generate email confirmation token too.