private void UpdateLineNumbers()

in src/TimeStampMargin/TimeStampMargin.cs [203:284]
69 lines of code
13 McCabe index (conditional complexity)

        private void UpdateLineNumbers()
        {
            HashSet<object> visibleLines = new HashSet<object>();
            foreach (var line in _textView.TextViewLines)
            {
                if (line.IsFirstTextViewLineForSnapshotLine)
                {
                    visibleLines.Add(line.IdentityTag);
                }
            }

            //Go backwards through the list so we remove no-longer-visible children back-to-front.
            Dictionary<object, TimeStampVisual> visibleTags = new Dictionary<object, TimeStampVisual>();
            List<int> childrenToRemove = new List<int>();

            for (int i = _translatedCanvas.Children.Count - 1; (i >= 0); --i)
            {
                TimeStampVisual visual = _translatedCanvas.Children[i] as TimeStampVisual;
                if (visual != null)
                {
                    if (visibleLines.Contains(visual.LineTag))
                    {
                        visibleTags.Add(visual.LineTag, visual);
                    }
                    else
                    {
                        childrenToRemove.Add(i);
                    }
                }
                else
                {
                    Debug.Fail("Wrong type of child");
                }
            }

            List<TimeStampVisual> newVisuals = new List<TimeStampVisual>();
            foreach (var line in _textView.TextViewLines)
            {
                if (line.IsFirstTextViewLineForSnapshotLine)
                {
                    int lineNumber = line.Start.GetContainingLine().LineNumber;
                    if (lineNumber < _lineTimeStamps.Count)             // No time stamp for the last line in the file.
                    {
                        var timeStamp = _lineTimeStamps[lineNumber];
                        TimeStampVisual visual;

                        if (!visibleTags.TryGetValue(line.IdentityTag, out visual))
                        {
                            int i = childrenToRemove.Count - 1;

                            if (i < 0)
                            {
                                visual = new TimeStampVisual();
                                newVisuals.Add(visual);
                            }
                            else
                            {
                                visual = _translatedCanvas.Children[childrenToRemove[i]] as TimeStampVisual;
                                Debug.Assert(visual != null);

                                // Don't remove child from canvas.
                                childrenToRemove.RemoveAt(i);
                            }
                        }

                        // Draw visual on text view.
                        visual.UpdateVisual(timeStamp, line, _textView, _formatting, base.MinWidth, _oldViewportTop, _showHours, _showMilliseconds);
                    }
                }
            }

            // Remove all the remaining unused children.
            foreach (int i in childrenToRemove)
            {
                _translatedCanvas.Children.RemoveAt(i);
            }

            foreach (var visual in newVisuals)
            {
                _translatedCanvas.Children.Add(visual);
            }
        }