Question

I have a third party service from which I’m getting a large collection of data and I want to store that information in my local database. Suppose I have 3 tables in my database User, Role and UserRole.

1. User table contains the following fields – UserId(PK), UserName.
2. Role table contains the following fields – RoleId(PK), RoleName.
3. UserRole table contains the following fields – UserId(FK),RoleId(FK).

So there is a Many To Many relationship between User and Role table.

When I try to save the following records to database its generating duplicate records in Role table.

using (CFAContext context = new CFAContext())
{
    context.Users.Add(new User { UserName = "User 1", Roles = new List<Role> { new Role { RoleName = "Role 1" }, new Role { RoleName = "Role 2" }, new Role { RoleName = "Role 3" } } });
    context.Users.Add(new User { UserName = "User 2", Roles = new List<Role> { new Role { RoleName = "Role 1" }, new Role { RoleName = "Role 2" } } });
    context.Users.Add(new User { UserName = "User 3", Roles = new List<Role> { new Role { RoleName = "Role 1" }, new Role { RoleName = "Role 4" } } });
    context.SaveChanges();
}

How can I insert this list to database(User and Role) without any duplicate records in User and Role table ?

Answer 1

I guess the RoleId fields are unique identifiers, thus for each role you have added, you will get a new record in the database with different RoleId fields as you are creating a new Role instance.

If you change your code to the following it will work;

Role role1 = new Role { RoleName = "Role 1" }
Role role2 = new Role { RoleName = "Role 2" }
Role role3 = new Role { RoleName = "Role 3" }
Role role4 = new Role { RoleName = "Role 4" }

context.Users.Add(new User { UserName = "User 1", Roles = new List<Role> { role1, role2, role3 } });
    context.Users.Add(new User { UserName = "User 2", Roles = new List<Role> { role1,role2 } });
    context.Users.Add(new User { UserName = "User 3", Roles = new List<Role> { role1, role4 } });
    context.SaveChanges();