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POFaster alternative to DateTime.ParseExact
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copied!<p>I parse a string into a DateTime millions of times:</p> <pre><code>public static CultureInfo ci = CultureInfo.InvariantCulture; while (!reader.EndOfStream) { line = reader.ReadLine(); string[] fields = line.Split(' '); DateTime newDT = DateTime.ParseExact(fields[0], "yyyyMMddTHHmmssfff", ci); } </code></pre> <p>My profiler highlights ParseExact as being a huge part of time taken. Is there any other method/approach that could parse the string into a DateTime that would be faster?</p> <p>FOLLOW UP1:</p> <p>1) I tried this - but speed was same</p> <pre><code>bool OK = DateTime.TryParseExact(fields[0], "yyyyMMddTHHmmssfff", null, System.Globalization.DateTimeStyles.None,out DT); </code></pre> <p>2)</p> <p>I tried to code my own parser - but this too was as slow:</p> <pre><code>public static DateTime fastParse(ref string s) { return new DateTime(int.Parse(s.Substring(0,4)), int.Parse(s.Substring(4,2)),int.Parse(s.Substring(6,2)), int.Parse(s.Substring(9,2)),int.Parse(s.Substring(11,2)),int.Parse(s.Substring(13,2)),int.Parse(s.Substring(15, 3))); } </code></pre> <p>FOLLOW UP2</p> <p>I tried Master117 suggestion of storing values - AGAIN it is NO faster - perhaps the issue is the construction?</p> <pre><code> public class fastParseData { int year; int mon; int day; int hour; int min; string previousSlice = ""; public DateTime fastParse(ref string s) { if (previousSlice != s.Substring(0, 12)) { year=int.Parse(s.Substring(0,4)); mon=int.Parse(s.Substring(4,2)); day=int.Parse(s.Substring(6,2)); hour= int.Parse(s.Substring(9,2)); min = int.Parse(s.Substring(11,2)); previousSlice = s.Substring(0, 12); } return new DateTime(year, mon, day, hour,min, int.Parse(s.Substring(13, 2)), int.Parse(s.Substring(15, 3))); } } </code></pre> <p>FOLOW UP3</p> <pre><code> public class fastParseData { int year; int mon; int day; int hour; int min; string previousSlice = ""; DateTime previousDT; public DateTime fastParse(ref string s) { if (previousSlice != s.Substring(0, 12)) { year=int.Parse(s.Substring(0,4)); mon=int.Parse(s.Substring(4,2)); day=int.Parse(s.Substring(6,2)); hour= int.Parse(s.Substring(9,2)); min = int.Parse(s.Substring(11,2)); previousSlice = s.Substring(0, 12); previousDT = new DateTime(year, mon, day, hour,min,0,0); } return previousDT.AddMilliseconds((int.Parse(s.Substring(13, 2))*1000)+int.Parse(s.Substring(15, 3))); } } </code></pre> <p>FOLLOW UP4</p> <p>From my profiler the crux seems to be </p> <pre><code>int.Parse(s.Substring(13, 2)) </code></pre> <p>With the Parse bit being more costly than the substring.</p> <p>I tried </p> <pre><code>int.TryParse(s.Substring(13, 2),NumberStyles.None,ci, out secs) Convert.ToInt32(s.Substring(13, 2)); </code></pre> <p>but again - no difference in speed.</p> <p>Is there a faster way to parse an int?</p>

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