I have POCO like these:
public class Student
{
public int StudentId { get; set; }
public string Name { get; set; }
public Level Level { get; set; }
}
public class Level
{
public int LevelId { get; set; }
public string Name { get; set; }
public ICollection<Student> Students { get; set; }
}
And here is how I'm saving all students in a single level:
public void InsertAllFirstLevelStudents(List<Student> students)
{
// Here all students belong to the same level
var level = Utils.GetFirstLevel();
students.ForEach(s => s.Level = level);
context.Students.AddRange(students);
context.SaveChanges();
}
But when saving, I get this error:
entity object cannot be referenced by multiple instances of IEntityChangeTracker
When I fetch the same level individually like: context.Levels.FirstOrDefault(l=> l.Name == "First"); , there is no problem, but of course, it then executes separate db queries to which is what I'm trying to avoid.
What can be done for this ?
public class Student
{
public int StudentId { get; set; }
public LevelId {get; set;}
public string Name { get; set; }
[ForeignKey("LevelId")]
public Level Level { get; set; }
}
and then
students.ForEach(s => s.LevelId = level.LevelId);
You can just add the student to the Students
collection of the level.
// Here all students belong to the same level
var level = Utils.GetFirstLevel();
foreach (var student in students) {
level.Students.Add(student);
}
context.Students.AddRange(students); // Probably not necessary
context.SaveChanges();
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