简单的 emit expression and reflected 性能比较

class Student
{            
    public string Name { get; set; }
}

static double Test(int loop, Student stu, Func<Student, string> action)
{
    var watch = Stopwatch.StartNew();
    string s = null;
    for (var i = 0; i < loop; i++)
        s = action(stu);

    return watch.ElapsedTicks;
}

static Func<Student, string> NativeGetter()
{
    return s => s.Name;
}

static Func<Student, string> ReflectedGetter()
{
    var type = typeof (Student);
    var prop = type.GetProperty("Name");

    return s => (string)prop.GetValue(s, null);                       
}

static Func<Student, string> EmittedGetter()
{
    var dm = new DynamicMethod(name: "EmittedGetter", returnType: typeof(string), parameterTypes: new[] { typeof(Student) }, owner: typeof(Student));

    var type = typeof (Student);
    var prop = type.GetMethod("get_Name");
    var il = dm.GetILGenerator();
    il.Emit(OpCodes.Ldarg_0);
    il.Emit(OpCodes.Call, prop);
    il.Emit(OpCodes.Ret);

    return (Func<Student, string>)dm.CreateDelegate(typeof(Func<Student, string>));
}

static Func<Student, string> ExpressionGetter()
{
    var type = typeof(Student);
    var prop = type.GetMethod("get_Name");

    ParameterExpression pa = Expression.Parameter(typeof(Student));
    Expression body = Expression.Call(pa, prop);

    return Expression.Lambda<Func<Student, string>>(body, pa).Compile();
}

static Func<Student, string> DynamicGetter()
{
    return s => { dynamic d = s; return d.Name; };
}

[MethodImpl(MethodImplOptions.NoOptimization)]
public static void Run()
{
    const int loop = 5000000;

    var stu = new Student {Name = "Mike"};

    var dynamic =
        Test(loop, stu, DynamicGetter());

    var expression =
        Test(loop, stu, ExpressionGetter());

    var native = 
        Test(loop, stu, NativeGetter());

    var emitted =
        Test(loop, stu, EmittedGetter());                        
            
    var reflected =
        Test(loop, stu, ReflectedGetter());           

    Console.WriteLine("native:{0}\ndynamic:{1}\nemit:{2}\nexpression:{3}\nreflection:{4}", 1, dynamic / native, emitted / native, expression / native, reflected / native);

    Console.ReadKey();
}