Question

This should be a simple one involving EF Code first but I can’t wrap my head around the documentation and all the examples I am finding are from older versions. I am working with the latest (4.1).

Anyway I have some models like:

public class Foo
{
    public int ID { get; set; }
    public Bar Bar { get; set; }
}

public class Bar
{
    public int ID { get; set; }
    public string Value { get; set; }
}

I used some scaffolding with Asp.Net MVC to create my controllers/repositories and when I create a ‘Foo’ object, it also creates a ‘Bar’ object even though I set the ‘Bar’ property from something stored in the database.

public class FooViewModel
{
    public int ID { get; set; }
    public int BarID { get; set; }
}

public ActionResult Create(FooViewModel foo)
{
    var entity = new Foo()
        {
            ID = foo.ID,
            Bar = _barRepository.Find(foo.BarID)
        };
    _fooRepository.InsertOrUpdate(entity);
    _fooRepository.Save();
    // more stuff
}

How can I use fluent syntax for EF in order to stop it from creating a new ‘Bar’ row in the database?

Update

Here is the generated repository code:

    public void InsertOrUpdate(Foo foo)
    {
        if (foo.ID == default(int)) {
            // New entity
            context.Foo.Add(foo);
        } else {
            // Existing entity
            context.Foo(foo).State = EntityState.Modified;
        }
    }

    public void Save()
    {
        context.SaveChanges();
    }

Answer 1

your _fooRepository and _barRepository need to share same DB context instance. If the are using two instances the Bar will be in added state.