A referential integrity constraint violation occurred

Seems like you have some relationship with foreign key field and a navigation property in the item, and those fields have conflicting values. This occurs when you load an entity and its related entities, change the relationship at one end, mark only that end as Modified and attempt to save. Make sure you modify relationship at both ends and mark all the affected entities as Modified before calling SaveChanges.

I encountered this exception under a different set of circumstances, and am posting here since this question comes up when the error message is searched.

The exception was thrown when calling IObjectContextAdapter.ObjectContext.AttachTo(entitySetName, entity) with a partially-loaded entity. The foreign keys on the entity were defined, but the navigational properties were not loaded. (That is, O.ItemID had a value, but O.Item was null). The specific circumstances did not allow O.Item to be loaded.

The problem turned out to be that the Object State Manager had loaded the object in a separate method and was already tracking the object defined with the same keys. Since the separate method did not need to track the object state, the issue was resolved by calling IQueryable.AsNoTracking() within that method.

What is the definition of the item object? It seems that in some of its collections that set the realionship with other entities exist some type of conflict. You could try to clear all the collections to see if the problem persists, but in this case you lost the foreign key assignment. But perhaps it could help you to locate the problem.

This could be a tip. When I try to attach an existing entity to the context, I use to do the following:

mMaMDBEntities.Entry<MamConfiguration>(item).State = System.Data.EntityState.Modified;

You can add the using of System.Data to avoid the needed to write it all the time.

This attach the entity in the state that you want, modified in this case and track the changes. This is one line instead of two.