DatabaseContext delay to update database - wpf

Question

I have an issue when I use Code First EF. When I want to insert an User with its Permissions, the user insert well, but in inserting Permissions just after insert user, I see this exception :
SqlException: The INSERT statement conflicted with the FOREIGN KEY constraint "FK_dbo.UserPermissions_dbo.Users_UserId". The conflict occurred in database "DATABASE", table "dbo.Users", column 'UserId'.
Here my code :
public class User
{
public short UserId { get; set; }
public string Username { get; set; }
public string Password { get; set; }
public ObservableCollection<UserPermission> UserPermissions { get; set; }
}
public class UserPermission
{
public int UserPermissionId { get; set; }
public short UserId { get; set; }
public short PermissionEnum { get; set; }
public bool IsPermitted { get; set; }
}
public class DatabaseContext : DbContext
{
public DatabaseContext()
{
}
public DbSet<User> Users { get; set; }
public DbSet<UserPermission> UserPermissions { get; set; }
}
And final code to insert is :
private void ConfirmButton_Click(object sender, RoutedEventArgs e)
{
var user = new User { Username = "myUsername", Password = "12"};
using (var dbContext = new DatabaseContext())
{
dbContext.Users.AddOrUpdate(user);
dbContext.SaveChanges();
}
SaveUserPermissions(user);
}
private void SaveUserPermissions(User user)
{
var userPermissionsToSave = new ObservableCollection<UserPermission>();
foreach (var permission in ThisUserPermissionData.UserPermissions)
{
var newUserPermission = new UserPermission();
newUserPermission.UserId = PageModel.UserId;
newUserPermission.UserPermissionTypeEnum = 4;
userPermissionsToSave.Add(newUserPermission);
}
using (var dbContext = new DatabaseContext())
{
dbContext.UserPermissions.AddOrUpdate(userPermissionsToSave.ToArray());
dbContext.SaveChanges();
}
}
Note that when I set breakpoint after save user, the code perform correctly. But in normal mode, my code has that exception.
Thanks in advance.