崇言崇語

根據上篇 如果我們可以用 try..catch 來解決 int.Parse 出現的exception 問題, 那為何需要用 int.TryParse ? 答案是＂效能＂！ 底下範例使用 Stopwatch 來測試 Parse 跟 TryParse 的效能 Sample:

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int iNum; Stopwatch sw = null; long ticks; // int.Parse Success sw = Stopwatch.StartNew(); for (int i = 1; i < 1000; i++) { try { iNum = int.Parse("123"); } catch (Exception) { iNum = 0; } } sw.Stop(); ticks = sw.ElapsedTicks; // Total Ticks Response.Write("int.Parse() : Success, Total " + ticks + " ticks
"); // int.TryParse Success sw = Stopwatch.StartNew(); for (int i = 1; i < 1000; i++) { if (!int.TryParse("123", out iNum)) { iNum = 0; } } sw.Stop(); ticks = sw.ElapsedTicks; // Total Ticks Response.Write("int.TryParse() : Success, Total " + ticks + " ticks
"); // int.TryParse Fail sw = Stopwatch.StartNew(); for (int i = 1; i < 1000; i++) { try { iNum = int.Parse("abc"); } catch (Exception) { iNum = 0; } } sw.Stop(); ticks = sw.ElapsedTicks; // Total Ticks Response.Write("int.Parse() : Fail, Total " + ticks + " ticks
"); // int.TryParse Fail sw = Stopwatch.StartNew(); for (int i = 1; i < 1000; i++) { if (!int.TryParse("abc", out iNum)) { iNum = 0; } } sw.Stop(); ticks = sw.ElapsedTicks; // Total Ticks Response.Write("int.TryParse() : Fail, Total " + ticks + " ticks
"); Output:

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int.Parse() : Success, Total 971 ticks int.TryParse() : Success, Total 944 ticks int.Parse() : Fail, Total 481736 ticks int.TryParse() : Fail, Total font color="green">822 ticks 數據上看來, 兩種方式在發生exception時, 處理的時間竟然差了幾百倍 除非程式不會出現Exception (??), 否則應該要使用TryParse, 程式碼也較精簡.