How can the enumerator encapsulate an array

Question

I have an array of object with the starting length of 4, and each time the Add method reaches the length, the length doubles. The array implements IEnumerable:

 public ObjectArrayCollection()
    {
        this.objectArray = new object[ObjectArrayCapacity];
        Count = 0;
    }

    public int Count { get; protected set; }

    public object this[int index]
    {
        get => this.objectArray[index];
        set => this.objectArray[index] = value;
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    public ObjectArrayEnumeration GetEnumerator()
    {
        return new ObjectArrayEnumeration(objectArray);
    }

and a class that implements IEnumeration:

 public ObjectArrayEnumeration(object[] objectArray)
    {
        this.objectArray = objectArray;
    }
    public object Current
    {
        get
        {
            try
            {
                return objectArray;
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }
    public bool MoveNext()
    {
        position++;
        return position < objectArray.Length;
    }
    public void Reset()
    {
        position = -1;
    }

The "possition < objectArray.length" condition is not good since objectArray can contain null if objects added don't fill the array. I sent the Count to the enumerator:

public ObjectArrayEnumeration GetEnumerator()
    {
        return new ObjectArrayEnumeration(objectArray, Count);
    }

but since I need them both I was told that the enumerator should encapsulate objectArray. I've tried this:

public IEnumerator GetEnumerator()
    {
        return objectArray.GetEnumerator();
    }

but this way I don't enumerate the values. I am new with C# and learning and I've run out of ideas. How can the enumerator encapsulate the objectArray?