Update and Add Child Rows at same time with Entity Framework

Question

i´m having some troubles when it comes to modify and add child rows at the same time. I´m using the technique from the answer: stackoverflow.com/questions/5557829/....

The problem is in the following code:

public void EditReport(tbl_inspection inspection)
{
    foreach (var roll in inspection.tbl_inspection_roll)
    {                    
        container.tbl_inspection_roll.Attach(roll);
        container.ObjectStateManager.ChangeObjectState(roll, (roll.id_inspection_roll == 0) ? EntityState.Added : EntityState.Modified);
    }

    container.SaveChanges();
}

I always have at least 1 row to update. When I have 1 row to add, it works fine, the problem is when I try to add more than 1 row at the same time, shows the well-known error:

An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.

Feels like I´m missing something here...

Answer 1

I think that you need to split off the modified from the added. In the question that you linked to Ladislav had the following code as an example of this:

if (myEntity.Id != 0)
{
    context.MyEntities.Attach(myEntity);
    context.ObjectStateManager.ChangeObjectState(myEntity, EntityState.Modified);
}
else
{
    context.MyEntities.AddObject(myEntity);
}

context.SaveChanges();

I think that using Attach specifically, instead of using AddObject is what's causing the error.

EDIT: Try the following for the Attach part instead:

var r = new tbl_inspection_roll { id_inspection_roll = roll.id_inspection_roll };
container.tbl_inspection_roll.Attach(r);
container.Entry(r).CurrentValues.SetValues(roll);

Answer 2

The problem here is because two or more child stubs have the same key: 0. Once you try to Attach the first object, it fires the error.

The method will have to be redesigned, using some kind of DTO (I think it's not correct to pass the ViewModel object to the Domain Model layer, thats why I was using stubs). Or calling a function to Add/Modify direct from the Controller.

EDIT:

Here's the code:

public void EditReport(Inspection obj)
{
    var inspection = new tbl_inspection
    {
        id_inspection = obj.ID,
        code = obj.Code       
    };

    foreach (var roll in obj.Rolls)
    {                    
        var rollStub = new tbl_inspection_roll
        {
            id_inspection_roll = roll.ID,
            id_inspection = obj.ID,
            description = roll.Description
        };

        container.tbl_inspection_roll.Attach(roll);
        container.ObjectStateManager.ChangeObjectState(roll, (roll.id_inspection_roll == 0) ? EntityState.Added : EntityState.Modified);
    }

    container.tbl_inspection.Attach(inspection);
    container.ObjectStateManager.ChangeObjectState(inspection, EntityState.Modified);

    container.SaveChanges();
}

Any better solutions are welcomed...

Answer 3

If I understand you problem correctly, you are trying to save an object graph containing a ParentObject and related ChildObjects and you're getting the exception because Attach() is not able to reconcile Id collisions among the ChildObjects in the database and the attached ParentObject.

Below is a work around I've used in the past. It's not pretty but it gets the job done.

public ParentObject Upsert(ParentObject newParentObject)
{
    // Check for an existing ParentObject.
    ParentObject exisitingParentObject = container.ParentObjects.SingleOrDefault(o => o.Id == newParentObject.Id);

    // If not an existing ParentObject
    if (exisitingParentObject == null)
    {
        // Add a new ParentObject
        exisitingParentObject = container.ParentObjects.Add(container.ParentObjects.Create());
    }

    // Update the properties of the existing ParentObject with the values of the new ParentObject
    var parentEntry = container.Entry(exisitingParentObject);
    parentEntry.CurrentValues.SetValues(newParentObject);

    // Remove ChildObjects that are in the existing but not in the new.
    for (int i = exisitingParentObject.ChildObjects.Count() - 1; i >= 0; i--)
    {
        ChildObject exisitingChildObject = exisitingParentObject.ChildObjects[i];
        if (!newParentObject.ChildObjects.Any(o => o.Id == exisitingChildObject.Id))
        {
            container.ChildObjects.Remove(exisitingChildObject);
        }
    }

    // Upsert new ChildObjects
    foreach (ChildObject newChildObject in newParentObject.ChildObjects)
    {
        // Check for an existing ChildObject
        ChildObject exisitingChildObject = exisitingParentObject.SingleOrDefault(o => o.Id == newChildObject.Id);

        // If not an existing ChildObject
        if (exisitingChildObject == null)
        {
            // Add a new ChildObject
            exisitingChildObject = exisitingParentObject.ChildObjects.Add(container.ChildObject.Create());
        }

        var childEntry = container.Entry(exisitingChildObject);
        childEntry.CurrentValues.SetValues(newChildObject);
    }

    container.SaveChanges();

    return exisitingParentObject;
}