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copied!<p>Ok so I was chatting about this with someone and decided to test this more. As far as I can tell, the performance of <code>as</code> and <code>is</code> are both very good, compared to testing your own member or function to store type information.</p> <p>I used <code>Stopwatch</code>, which I just learned may not be the most reliable approach, so I also tried <code>UtcNow</code>. Later, I also tried Processor time approach which seems similar to <code>UtcNow</code> including unpredictable create times. I also tried making the base class non-abstract with no virtuals but it didn't seem to have a significant effect.</p> <p>I ran this on a Quad Q6600 with 16GB RAM. Even with 50mil iterations, the numbers still bounce around +/- 50 or so millisec so I wouldn't read too much into the minor differences.</p> <p>It was interesting to see that x64 created faster but executed as/is slower than x86</p> <p><strong>x64 Release Mode:</strong> <br /> Stopwatch: <br /> As: 561ms<br /> Is: 597ms<br /> Base property: 539ms<br /> Base field: 555ms<br /> Base RO field: 552ms<br /> Virtual GetEnumType() test: 556ms<br /> Virtual IsB() test: 588ms<br /> Create Time : 10416ms<br /></p> <p>UtcNow: <br /> As: 499ms<br /> Is: 532ms<br /> Base property: 479ms<br /> Base field: 502ms<br /> Base RO field: 491ms<br /> Virtual GetEnumType(): 502ms<br /> Virtual bool IsB(): 522ms<br /> Create Time : 285ms (This number seems unreliable with UtcNow. I also get 109ms and 806ms.) <br /></p> <p><strong>x86 Release Mode:</strong><br /> Stopwatch: <br /> As: 391ms<br /> Is: 423ms<br /> Base property: 369ms<br /> Base field: 321ms<br /> Base RO field: 339ms<br /> Virtual GetEnumType() test: 361ms<br /> Virtual IsB() test: 365ms<br /> Create Time : 14106ms<br /></p> <p>UtcNow: <br /> As: 348ms<br /> Is: 375ms<br /> Base property: 329ms<br /> Base field: 286ms<br /> Base RO field: 309ms<br /> Virtual GetEnumType(): 321ms<br /> Virtual bool IsB(): 332ms<br /> Create Time : 544ms (This number seems unreliable with UtcNow.)<br /></p> <p>Here's most of the code:</p> <pre><code> static readonly int iterations = 50000000; void IsTest() { Process.GetCurrentProcess().ProcessorAffinity = (IntPtr)1; MyBaseClass[] bases = new MyBaseClass[iterations]; bool[] results1 = new bool[iterations]; Stopwatch createTime = new Stopwatch(); createTime.Start(); DateTime createStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { if (i % 2 == 0) bases[i] = new MyClassA(); else bases[i] = new MyClassB(); } DateTime createStop = DateTime.UtcNow; createTime.Stop(); Stopwatch isTimer = new Stopwatch(); isTimer.Start(); DateTime isStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { results1[i] = bases[i] is MyClassB; } DateTime isStop = DateTime.UtcNow; isTimer.Stop(); CheckResults(ref results1); Stopwatch asTimer = new Stopwatch(); asTimer.Start(); DateTime asStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { results1[i] = bases[i] as MyClassB != null; } DateTime asStop = DateTime.UtcNow; asTimer.Stop(); CheckResults(ref results1); Stopwatch baseMemberTime = new Stopwatch(); baseMemberTime.Start(); DateTime baseStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { results1[i] = bases[i].ClassType == MyBaseClass.ClassTypeEnum.B; } DateTime baseStop = DateTime.UtcNow; baseMemberTime.Stop(); CheckResults(ref results1); Stopwatch baseFieldTime = new Stopwatch(); baseFieldTime.Start(); DateTime baseFieldStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { results1[i] = bases[i].ClassTypeField == MyBaseClass.ClassTypeEnum.B; } DateTime baseFieldStop = DateTime.UtcNow; baseFieldTime.Stop(); CheckResults(ref results1); Stopwatch baseROFieldTime = new Stopwatch(); baseROFieldTime.Start(); DateTime baseROFieldStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { results1[i] = bases[i].ClassTypeField == MyBaseClass.ClassTypeEnum.B; } DateTime baseROFieldStop = DateTime.UtcNow; baseROFieldTime.Stop(); CheckResults(ref results1); Stopwatch virtMethTime = new Stopwatch(); virtMethTime.Start(); DateTime virtStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { results1[i] = bases[i].GetClassType() == MyBaseClass.ClassTypeEnum.B; } DateTime virtStop = DateTime.UtcNow; virtMethTime.Stop(); CheckResults(ref results1); Stopwatch virtMethBoolTime = new Stopwatch(); virtMethBoolTime.Start(); DateTime virtBoolStart = DateTime.UtcNow; for (int i = 0; i < iterations; i++) { results1[i] = bases[i].IsB(); } DateTime virtBoolStop = DateTime.UtcNow; virtMethBoolTime.Stop(); CheckResults(ref results1); asdf.Text += "Stopwatch: " + Environment.NewLine + "As: " + asTimer.ElapsedMilliseconds + "ms" + Environment.NewLine +"Is: " + isTimer.ElapsedMilliseconds + "ms" + Environment.NewLine + "Base property: " + baseMemberTime.ElapsedMilliseconds + "ms" + Environment.NewLine + "Base field: " + baseFieldTime.ElapsedMilliseconds + "ms" + Environment.NewLine + "Base RO field: " + baseROFieldTime.ElapsedMilliseconds + "ms" + Environment.NewLine + "Virtual GetEnumType() test: " + virtMethTime.ElapsedMilliseconds + "ms" + Environment.NewLine + "Virtual IsB() test: " + virtMethBoolTime.ElapsedMilliseconds + "ms" + Environment.NewLine + "Create Time : " + createTime.ElapsedMilliseconds + "ms" + Environment.NewLine + Environment.NewLine+"UtcNow: " + Environment.NewLine + "As: " + (asStop - asStart).Milliseconds + "ms" + Environment.NewLine + "Is: " + (isStop - isStart).Milliseconds + "ms" + Environment.NewLine + "Base property: " + (baseStop - baseStart).Milliseconds + "ms" + Environment.NewLine + "Base field: " + (baseFieldStop - baseFieldStart).Milliseconds + "ms" + Environment.NewLine + "Base RO field: " + (baseROFieldStop - baseROFieldStart).Milliseconds + "ms" + Environment.NewLine + "Virtual GetEnumType(): " + (virtStop - virtStart).Milliseconds + "ms" + Environment.NewLine + "Virtual bool IsB(): " + (virtBoolStop - virtBoolStart).Milliseconds + "ms" + Environment.NewLine + "Create Time : " + (createStop-createStart).Milliseconds + "ms" + Environment.NewLine; } } abstract class MyBaseClass { public enum ClassTypeEnum { A, B } public ClassTypeEnum ClassType { get; protected set; } public ClassTypeEnum ClassTypeField; public readonly ClassTypeEnum ClassTypeReadonlyField; public abstract ClassTypeEnum GetClassType(); public abstract bool IsB(); protected MyBaseClass(ClassTypeEnum kind) { ClassTypeReadonlyField = kind; } } class MyClassA : MyBaseClass { public override bool IsB() { return false; } public override ClassTypeEnum GetClassType() { return ClassTypeEnum.A; } public MyClassA() : base(MyBaseClass.ClassTypeEnum.A) { ClassType = MyBaseClass.ClassTypeEnum.A; ClassTypeField = MyBaseClass.ClassTypeEnum.A; } } class MyClassB : MyBaseClass { public override bool IsB() { return true; } public override ClassTypeEnum GetClassType() { return ClassTypeEnum.B; } public MyClassB() : base(MyBaseClass.ClassTypeEnum.B) { ClassType = MyBaseClass.ClassTypeEnum.B; ClassTypeField = MyBaseClass.ClassTypeEnum.B; } } </code></pre>

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