How to Implement Upsert Logic Using Entity Framework?

Update or Insert Logic with Entity Framework

Entity Framework provides multiple approaches for managing the "update row if it exists, else insert new row" scenario.

Attached Objects:

If the entity being modified is already attached to the context, it can be directly updated:

if (context.ObjectStateManager.GetObjectStateEntry(myEntity).State == EntityState.Detached)
{
    context.MyEntities.AddObject(myEntity);
}

// Attached object tracks modifications automatically

context.SaveChanges();

Non-Attached Objects with Known Key:

If the entity has a non-zero key (indicating an existing entry), it can be attached and modified as follows:

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

context.SaveChanges();

Non-Attached Objects with Unknown Key:

In cases where the key is unknown, a lookup query can be performed to determine existence:

var id = myEntity.Id;
if (context.MyEntities.Any(e => e.Id == id))
{
    context.MyEntities.Attach(myEntity);
    context.ObjectStateManager.ChangeObjectState(myEntity, EntityState.Modified);
}
else
{
    context.MyEntities.AddObject(myEntity);
}

context.SaveChanges();

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