Question

I have a class which has two HashSet<String> collections as private members. Other classes in my code would like to be able to iterate over those HashSets and read their contents. I don’t want to write a standard getter because another class could still do something like myClass.getHashSet().Clear(); Is there any other way to expose the elements of my HashSets to iteration without exposing the reference to the HashSet itself? I’d love to be able to do this in a way that is compatible with for-each loops.

Answer 1

Expose a IEnumerable<T> property:

public IEnumerable<whatevertype> MyHashSet {
    get {
        return this.myHashSet;
    }
}

Of course, the user of this code can cast that IEnumerable<T> to a HashSet<T> and edit elements, so to be on the safe side (while hurting performance), you can do:

public IEnumerable<whatevertype> MyHashSet {
    get {
        return this.myHashSet.ToArray();
    }
}

or:

public IEnumerable<whatevertype> MyHashSet {
    get {
        foreach(var item in this.myHashSet) {
            yield return item;
        }
    }
}

A more performant method of protection, but less convenient to the caller, is to return an IEnumerator<T>:

public IEnumerator<whatevertype> GetMyHashSetEnumerator() {
    return this.myHashSet.GetEnumerator();
}