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Occasionally I like to spend some time looking at the .NET code just to see how things are implemented behind the scenes. I stumbled upon this gem while looking at the String.Equals method via Reflector. C# [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)] public override bool Equals(object obj) { string strB = obj as string; if ((strB == null) && (this != null)) { return false; } return EqualsHelper(this, strB); } IL .method public hidebysig virtual instance bool Equals(object obj) cil managed { .custom instance void System.Runtime.ConstrainedExecution.ReliabilityContractAttribute::.ctor(valuetype System.Runtime.ConstrainedExecution.Consistency, valuetype System.Runtime.ConstrainedExecution.Cer) = { int32(3) int32(1) } .maxstack 2 .locals init ( [0] string str) L_0000: ldarg.1 L_0001: isinst string L_0006: stloc.0 L_0007: ldloc.0 L_0008: brtrue.s L_000f L_000a: ldarg.0 L_000b: brfalse.s L_000f L_000d: ldc.i4.0 L_000e: ret L_000f: ldarg.0 L_0010: ldloc.0 L_0011: call bool System.String::EqualsHelper(string, string) L_0016: ret } What is the reasoning for checking this against null ? I have to assume there is purpose otherwise this probably would have been caught and removed by now.

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