Timespan extension (used for log)

TimespanExtensions.cs

 public static string ToReadableString(this TimeSpan timeSpan)
        {
            var sb = new StringBuilder(16);

            var isNeg = timeSpan.Ticks < 0;
            if (isNeg)
            {
                timeSpan = new TimeSpan(-timeSpan.Ticks);
            }

            var totalMilliseconds = timeSpan.TotalMilliseconds;
            var hasMilliseconds = timeSpan.Milliseconds != 0;
            var writeSeconds = timeSpan.Seconds != 0 || (hasMilliseconds && timeSpan.Minutes != 0);

            if (totalMilliseconds >= 1000)
            {
                if (timeSpan.Days != 0)
                {
                    sb.AppendFormat("{0}d ", timeSpan.Days);
                }

                var hasHours = timeSpan.Hours != 0;
                if (hasHours) sb.AppendFormat("{0}h", timeSpan.Hours);

                var b2 = timeSpan.Minutes != 0 || (timeSpan.Seconds != 0 && hasHours);
                if (b2)
                {
                    sb.AppendFormat(hasHours ? ":{0:00}" : "{0}m", timeSpan.Minutes);
                }

                if (writeSeconds)
                {
                    if (hasHours || b2)
                    {
                        sb.AppendFormat(":{0:00}", timeSpan.Seconds);
                    }
                    else
                    {
                        sb.Append(timeSpan.Seconds);
                    }
                }
            }

            var putMilliseconds = hasMilliseconds || sb.Length == 0;
            if (putMilliseconds)
            {
                if (sb.Length == 0)
                {
                    sb.AppendFormat("{0:0.###}", totalMilliseconds);
                }
                else
                {
                    sb.AppendFormat(writeSeconds ? ".{0:000}" : "{0:n0}", timeSpan.Milliseconds);
                }
            }

            if (writeSeconds)
            {
                sb.Append("s");
            }
            else if (putMilliseconds)
            {
                sb.Append("ms");
            }
            if (isNeg)
            {
                sb.Insert(0, "-");
            }

            return sb.ToString();
        }