MVC inserting multiple records instead of expected one - asp.net-mvc

Question

Let's say I have two models:
public class User
{
[Key]
public int UserId { get; set; }
public string Name { get; set; }
}
and
public class Friend
{
[Key]
public int FriendId { get; set; }
public User A { get; set; }
public User B { get; set; }
}
Let's say I only have 2 users in my database (ids: 1 (Jon) and 2 (Sam)). Now I insert into table friend like this:
db.Friends.Add(new Friend()
{
A = db.Users.Find(1),
B = db.Users.Where(u => u.UserId == 2).First()
});
db.SaveChanges();
Suddenly, I find a user (3, Sam) in a table user. What is the reasoning behind this? Not completely sure if relevant or not, but note that even if I make A and B fields virtual, nothing changes.
UPDATE
Finally found how to reproduce my problem. Apparently the problem isn't exactly the same as I described.
User a, b;
using (var db = new DbConnection())
{
a = db.Users.First(u => u.UserId == 1);
b = db.Users.First(u => u.UserId == 2);
}
using (var db = new DbConnection())
{
db.Friends.Add(new Friend()
{
A = a,
B = b
});
db.SaveChanges();
}
Now users will have 4 users. Does it mean that if I step out of transaction, I can no longer access the entities as if they were exactly the same items in the current transaction? Or maybe there is a way to make the program know that I am referring to the same item (because the ID is the same)?

Answer 1

Honestly tried the same steps as you described and everything work well.. Anyway my steps
Created a db context class derived from `DbContext'
public class EFContext : DbContext
{
public DbSet<Friend> Friends { get; set; }
public DbSet<User> Users { get; set; }
public EFContext(string connectionString)
: base(connectionString)
{
}
}
I use MSQL2008 Express with win auth so I created the Users table
using (var db = new EFContext(#"Data Source=yourMachineName\SQLEXPRESS2008;Initial Catalog=DBName;Integrated Security=True;MultipleActiveResultSets=True"))
{
db.Users.Add(new User()
{
UserId = 1,
Name = "John"
});
db.Users.Add(new User()
{
UserId = 2,
Name = "Sam"
});
db.SaveChanges();
}
I checked my db and found 2 records
After I created the Friends table
using(var db = new EFContext(#"Data Source=yourMachineName\SQLEXPRESS2008;Initial Catalog=DBName;Integrated Security=True;MultipleActiveResultSets=True"))
{
db.Friends.Add(new Friend()
{
A = db.Users.Find(1),
B = db.Users.Where(u => u.UserId == 2).First()
});
db.SaveChanges();
}
Again I got 1 record in the Friends table with columns FriendId=1, A_UserId=1, B_UserId=2.
I checked the Users table and I still have 2 records.
If I were you I would try my code in a separate app. If it works then please post here all steps which led you to this problem.