4、提取看似无用的委托变量，减少构造开销

using System;

namespace ShouldCode
{
    public class ShouldDelegateVariable
    {
        public void Should()
        {
            Action show = Show;
            for (int i = 0 ; i < 10 ; i++)
            {
                DoShow(show);
            }
            /*IL_0008: newobj instance void [mscorlib]System.Action::.ctor(object, native int)
            IL_000d: stloc.0
            IL_000e: ldc.i4.0
            IL_000f: stloc.1
            IL_0010: br.s IL_0020
        // loop start (head: IL_0020)
            IL_0012: nop
            IL_0013: ldarg.0
            IL_0014: ldloc.0
            IL_0015: call instance void ShouldCode.ShouldDelegateVariable::DoShow(class [mscorlib]System.Action)
            IL_001a: nop
            IL_001b: nop
            IL_001c: ldloc.1
            IL_001d: ldc.i4.1
            IL_001e: add
            IL_001f: stloc.1

            IL_0020: ldloc.1
            IL_0021: ldc.i4.s 10
            IL_0023: clt
            IL_0025: stloc.2
            IL_0026: ldloc.2
            IL_0027: brtrue.s IL_0012
        // end loop */
        }

        public void Not()
        {
            for (int i = 0 ; i < 10 ; i++)
            {
                DoShow(Show);
            }
            /*
        // loop start (head: IL_001e)
            IL_0005: nop
            IL_0006: ldarg.0
            IL_0007: ldarg.0
            IL_0008: ldftn instance void ShouldCode.ShouldDelegateVariable::Show()
            IL_000e: newobj instance void [mscorlib]System.Action::.ctor(object, native int)
            IL_0013: call instance void ShouldCode.ShouldDelegateVariable::DoShow(class [mscorlib]System.Action)
            IL_0018: nop
            IL_0019: nop
            IL_001a: ldloc.0
            IL_001b: ldc.i4.1
            IL_001c: add
            IL_001d: stloc.0

            IL_001e: ldloc.0
            IL_001f: ldc.i4.s 10
            IL_0021: clt
            IL_0023: stloc.1
            IL_0024: ldloc.1
            IL_0025: brtrue.s IL_0005
        // end loop */
        }
        public void DoShow(Action action)
        {
            action?.Invoke();
        }
        public void Show()
        {
            Console.WriteLine("看起来代码是一样的，其实涉及到内存分配问题！");
            Console.WriteLine("提取变量可以减少委托构造开销，注意多出的开销在 not 演示的 loop 范围里的 newobj ！");
        }
    }
}

 补充： newobj 指令为类型分配内存资源。一般都是 new。