C# Error Handling – Should Service Throw Exception or Return When No Items Specified for Deletion

cerror handlingexceptions

I have a piece of code that can be represented as:

public class ItemService {

    public void DeleteItems(IEnumerable<Item> items)
    {
        // Save us from possible NullReferenceException below.
        if(items == null)
            return;

        foreach(var item in items)
        {
            // For the purpose of this example, lets say I have to iterate over them.
            // Go to database and delete them.
        }
    }
}

Now I'm wondering if this is the right approach or should I throw exception. I can avoid exception, because returning would be the same as iterating over an empty collection, meaning, no important code is executed anyway, but on the other hand I'm possibly hiding problems somewhere in the code, because why would anyone want to call DeleteItems with null parameter? This may indicate that there is a problem somewhere else in the code.

This is a problem I usually have with methods in services, because most of them do something and don't return a result, so if someone passes invalid information then there is nothing for the service to do, so it returns.

Best Answer

These are two different questions.

Should you accept null? That depends on your general policy about null in the code base. In my opinion, banning null everywhere except where explicitly documented is a very good practice, but it's even better practice to stick to the convention your code base already has.

Should you accept the empty collection? In my opinion: YES, absolutely. It is much more effort to restrict all callers to non-empty collections than to do the mathematically right thing - even if it surprises some developers who are iffy with the concept of zero.

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