Question

If I had CurrencyId, I would do something like this:

 public void InsertOrUpdate(Currency entity)
        {
            if (entity.CurrencyId == default(int))
            {
                // New entity
                this.dbset.Add(entity);
            }
            else
            {
                // Existing entity
                this.context.Entry(entity).State = EntityState.Modified;
            }
        }

But I’m using a string CurrencyCode as a PK and I’d like to be able to Add or Edit it. So I have to check whether the CurrencyCode exists in the db or not. How do I do this?

Adding a new entity is ok, but if I try to Edit:

 public void InsertOrUpdate(Currency entity)
        {
            if (GetByCurrency(entity.CurrencyCode) == null)
            {
                // New entity
                this.dbset.Add(entity);
            }
            else
            {
                // Existing entity
                this.context.Entry(entity).State = EntityState.Modified;
            }
        }

public Currency GetByCurrency(string currencyCode)
{
    return this.dbset.Find(currencyCode);
}

I’m getting

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

in

this.context.Entry(entity).State = EntityState.Modified;

Answer 1

That’s because when you do the Find, it’s returning the object and keeping a copy in the cache. You are then adding a new copy, so there are two.

Instead, you do one of two things. You either modify the copy returned by the find, if you can assume that CurrencyCode == null means it doesn’t exist in the database, then just add it or attach it.

So, something like:

var currency = GetByCurrency(entity.CurrencyCode);

if (currency == null)
     this.dbset.Add(entity);
else
     currency.Something = entity.Something;