NullReferenceException in Seed Method of Configuration file

Question

I'm not exactly sure why my Seed method is throwing an exception.

Here is my code:

//Roles
           var roles = new List<Role>
            {
                new Role {RoleName = "Admin"},
                new Role {RoleName = "SuperAdmin"}
            };

            roles.ForEach(s => context.Roles.AddOrUpdate(p => p.RoleName, s));
            context.SaveChanges();


            //Adds the 2 superadmins from AD to DB
            Credentials.GetUserByUsername(context, "credentials1");
            Credentials.GetUserByUsername(context, "credentials2");
            context.SaveChanges();


//Add the superadmins to a List
            var superAdmins = new List<User>();
            User admin1 = context.Users.Where(p => p.Username == "credentials1").FirstOrDefault();
            User admin2 = context.Users.Where(p => p.Username == "crendetials2").FirstOrDefault();

            superAdmins.Add(admin1);
            superAdmins.Add(admin2);

//Find the SuperAdmin role in DB
            Role superAdminRole = context.Roles.Where(p => p.RoleName == "SuperAdmin").FirstOrDefault();

//Add the role to each user
            foreach (User user in superAdmins)
            {
                if (user != null)
                {
                    superAdminRole.Users.Add(user);     <---- This is throwing the exception
                    context.SaveChanges();

                }

            }

superAdminRole.Users.Add(user) is throwing the exception. I can see when debugging that both users and roles are found so I'm not sure why I'm getting the exception.

Is it too early to do this operation? I assumed my context was able to handle this operation at this point since both users and roles are in the DB.

One last detail: if I stop debugging at this point and run the application a second time, I don't get the exception and Roles are properly assigned. I would like to avoid having to run the Seed method twice though.

Let me guess: you use FirstOrDefault for superAdminRole but there is NOT such role so superAdminRole variable is null. A tipo: do not call SaveChanges() inside a loop. I'd first set a breakpoint, it's faster than post a question. — Adriano Repetti, May 05 '14 at 12:11
possible duplicate of [What is a NullReferenceException and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Adriano Repetti, May 05 '14 at 12:12
@Adriano, the OP said that `when debugging that both users and roles are found` — Andrew, May 05 '14 at 12:13
@Adriano Indeed I can see that both the role and Users objects are found at that point. — Orphu.of.io, May 05 '14 at 12:17
So what's first line of stack trace? There aren't so much variables involved there... — Adriano Repetti, May 05 '14 at 12:18
at MyDb.Migrations.Configuration.Seed(MyContext context) in c:\MyProj\Migrations\Configuration.cs:line 56 at System.Data.Entity.Migrations.DbMigrationsConfiguration`1.OnSeed(DbContext context) at System.Data.Entity.Migrations.DbMigrator.SeedDatabase() at System.Data.Entity.Migrations.Infrastructure.MigratorBase.SeedDatabase().... — Orphu.of.io, May 05 '14 at 12:23
@Andrew 'user.Roles' shows as null, even if user and superAdminRole themselves aren't. What does that mean? And yes, superAdminRole.Users is also null. (although I was expecting that since no users have been added to that role yet?) — Orphu.of.io, May 05 '14 at 12:41
do you have many to many relationship? how did you configure your relationship in modelbuilder? — Andrew, May 05 '14 at 12:43
@Andrew Yes I have a many to many relationship. I have it defined this way: HasMany(e => e.Roles) .WithMany(i => i.Users) .Map(t => t.MapLeftKey("UserId").MapRightKey("RoleId") .ToTable("User_Role")); — Orphu.of.io, May 05 '14 at 12:48
looks to be correct. Could you please try to take the context.SaveChanges out of the loop, does it make any difference? — Andrew, May 05 '14 at 13:19
ok, can you validate your model against your database? Are `UserId` and `RoleId` marked as keys? what is the entire code for configuration of your many-2-many relation? — Andrew, May 05 '14 at 13:29
They aren't marked as key. I had in mind that having a virtual property as such: public virtual ICollection Roles { get; set; } would automatically create a FK relationship to RoledID. Am I correct to think that? The same kind of collection can be found in Roles: public virtual ICollection Users { get; set; }. Since they are collections, I thought that putting FK such as public int? RoleId would not work. — Orphu.of.io, May 05 '14 at 13:35

score 0 · Answer 1 · answered May 05 '14 at 12:12

0

Replace following statement

superAdminRole.Users.Add(user);

with

user.Role = superAdminRole;

also take the context.SaveChanges() out of the foreach loop.

answered May 05 '14 at 12:12

Andrew

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the thing is that `superAdminRole.Users` are null. – Andrew May 05 '14 at 12:14
Roles in the User Model is a collection: public virtual ICollection Roles { get; set; }, hence why I used the Add method. Any other ways to do it? – Orphu.of.io May 05 '14 at 12:16
`superAdminRole.Users` this is null, isn't it? – Andrew May 05 '14 at 12:32

NullReferenceException in Seed Method of Configuration file

1 Answers1