System.Xml.Xsl.Runtime.UnionIterator.MoveNext C# (CSharp) Method

        public SetIteratorResult MoveNext(XPathNavigator nestedNavigator) {
            switch (this.state) {
                case IteratorState.InitLeft:
                    // Fetched node from left iterator, now get initial node from right iterator
                    this.navOther = nestedNavigator;
                    this.state = IteratorState.NeedRight;
                    return SetIteratorResult.InitRightIterator;

                case IteratorState.NeedLeft:
                    this.navCurr = nestedNavigator;
                    this.state = IteratorState.LeftIsCurrent;
                    break;

                case IteratorState.NeedRight:
                    this.navCurr = nestedNavigator;
                    this.state = IteratorState.RightIsCurrent;
                    break;

                case IteratorState.LeftIsCurrent:
                    // Just returned left node as current, so get new left
                    this.state = IteratorState.NeedLeft;
                    return SetIteratorResult.NeedLeftNode;

                case IteratorState.RightIsCurrent:
                    // Just returned right node as current, so get new right
                    this.state = IteratorState.NeedRight;
                    return SetIteratorResult.NeedRightNode;
            }

            // Merge left and right nodes
            if (this.navCurr == null) {
                // If both navCurr and navOther are null, then iteration is complete
                if (this.navOther == null)
                    return SetIteratorResult.NoMoreNodes;

                Swap();
            }
            else if (this.navOther != null) {
                int order = this.runtime.ComparePosition(this.navOther, this.navCurr);

                // If navCurr is positioned to same node as navOther,
                if (order == 0) {
                    // Skip navCurr, since it is a duplicate
                    if (this.state == IteratorState.LeftIsCurrent) {
                        this.state = IteratorState.NeedLeft;
                        return SetIteratorResult.NeedLeftNode;
                    }

                    this.state = IteratorState.NeedRight;
                    return SetIteratorResult.NeedRightNode;
                }

                // If navOther is before navCurr in document order, then swap navCurr with navOther
                if (order < 0)
                    Swap();
            }

            // Return navCurr
            return SetIteratorResult.HaveCurrentNode;
        }