三元运算符？：vs if ... else ..哪一个更快？ [英] Ternary operator ?: vs if…else ..which one is more faster ?

问题描述

Hii，





哪个更快，三元还是其他，



以及哪一个有利于维护

Hii ,


Which is is more faster , ternary or if else ,

and which one is good for maintain

ability of the code.

推荐答案

拿这个代码：

Taking this code:

bool rv;
string check = "";

if ( check == "not" )
{
    rv = false;
}
else
{
    rv = true;
}

rv = ( check == "not" ) ? false : true;

这将产生这个IL：

That will produce this IL:

.method family hidebysig 
	instance void Page_Load (
		object sender,
		class [mscorlib]System.EventArgs e
	) cil managed 
{
	// Method begins at RVA 0x2050
	// Code size 55 (0x37)
	.maxstack 2
	.locals init (
		[0] bool rv,
		[1] string check,
		[2] bool CS

4

0000
）

IL_0000：nop
IL_0001：ldstr
IL_0006：stloc.1
IL_0007：ldloc.1
IL_0008： ldstrnot
IL_000d：call bool [mscorlib] System.String :: op_Equality（string，string）
IL_0012：ldc.i4.0
IL_0013：ceq
IL_0015： stloc.2
IL_0016：ldloc.2
IL_0017：brtrue.s IL_001f

IL_0019：nop
IL_001a：ldc.i4.0
IL_001b： stloc.0
IL_001c：nop
IL_001d：br.s IL_0023

IL_001f：nop
IL_0020：ldc.i4.1
IL_0021：stloc.0
IL_0022：nop

IL_0023：ldloc.1
IL_0024：ldstrnot
IL_0029：call bool [mscorlib] System.String :: op_Equality（string，string）
IL_002e：brtrue.s IL_0033

IL_0030：ldc.i4.1
IL_0031：br.s IL_0034

IL_0033：ldc.i4.0

IL_0034：nop
IL_0035：stloc.0
IL_0036：ret
} //方法结束

0000 ) IL_0000: nop IL_0001: ldstr "" IL_0006: stloc.1 IL_0007: ldloc.1 IL_0008: ldstr "not" IL_000d: call bool [mscorlib]System.String::op_Equality(string, string) IL_0012: ldc.i4.0 IL_0013: ceq IL_0015: stloc.2 IL_0016: ldloc.2 IL_0017: brtrue.s IL_001f IL_0019: nop IL_001a: ldc.i4.0 IL_001b: stloc.0 IL_001c: nop IL_001d: br.s IL_0023 IL_001f: nop IL_0020: ldc.i4.1 IL_0021: stloc.0 IL_0022: nop IL_0023: ldloc.1 IL_0024: ldstr "not" IL_0029: call bool [mscorlib]System.String::op_Equality(string, string) IL_002e: brtrue.s IL_0033 IL_0030: ldc.i4.1 IL_0031: br.s IL_0034 IL_0033: ldc.i4.0 IL_0034: nop IL_0035: stloc.0 IL_0036: ret } // end of method

你可以通过一些指令看到三元部分更短......原因是if语句引入了一个局部变量仅在if块内部使用。

这种差异会让你获得一点点性能，恕我直言，如果不适合使用三元替换，我不能证明这一点！

You can see that the ternary part shorter by a few instructions...The reason is that if statement is introducing a local variable to use only inside the if block.
This difference will gain you a tiny bit of performance, that IMHO do not justify to use ternary replace if when it's not fit!

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