Nested existing entity is duplicated when saving parent

Question

I am having a problem where when I try to save a new entity that has existing entities nested. Instead of creating a relationship with existing entities it is duplicating them.

This is roughly my model:

public class Record
{
    public int ID { get; set; }
    public string RecordValue { get; set; }
    public virtual ICollection<AddressLine> AddressLines { get; set; }
}
public class AddressLine
{
    public int ID { get; set; }
    public string AddressLineValue { get; set; }
    public virtual ICollection<AddressLineType> AddressLineTypes { get; set; }
}
public class AddressLineType
{
    public int ID { get; set; }
    public string AddressLineTypeValue { get; set; }
}

I don't want any duplicate AddressLineTypes added so in my code I am doing something like this:

public void button1_Click(object sender, EventArgs e)
{

    Record r = new Record();
    r.RecordValue = "Record value";

    AddressLine al = new AddressLine();
    al.AddressLineValue = "Address line value";

    AddressLineType alt;
    using (var db = new MyDbContext())
    {
        alt = db.AddressLineTypes.Single(x => x.Value == "TypeValue");
    }

    al.AddressLineTypes.Add(alt);
    r.AddressLines.Add(al);

    SaveRecord(r);
}

public void SaveRecord(Record r)
{
    using (var db = new MyDbContext())
    {
        db.Records.Add(r);
        db.SaveChanges();
    }
}

I have hit a breakpoint before db.SaveChanges() and the AddressLineType ID is populated but it creates new entries in the database as if ID == 0.

How do I stop the existing AddressLineTypes duplicating on save?

Jeff S · Accepted Answer · 2015-09-08 03:53:17Z

2

Try using a single Context:

...    
using (var db = new MyDbContext())
        {
            alt = db.AddressLineTypes.Single(x => x.Value == "TypeValue");


            al.AddressLineTypes.Add(alt);
            r.AddressLines.Add(al);

            SaveRecord(r, db);
        }
    }

public void SaveRecord(Record r, MyDbContext db)
{
        db.Records.Add(r);
        db.SaveChanges();
}

answered Sep 8, 2015 at 3:53

Jeff S

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1 Comment

Guerrilla Over a year ago

Thanks, I'll see if I can get that to work. My logic is a bit strange as the data comes in by way of a listener so I am making a request then spinning a while loop checking a Dictionary index for the request token and grabbing the object from the value. I would have to move a lot of logic out of my listener to get that to work. I guess I need to refactor all the code, I was hoping for a quick way to make the nested entities save properly when detached from the context :(

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