Summarize example code called with expression numbers

Following the example of using expression trees to build delegates to improve reflection performance, I made a few small changes that are just right for my own use

    public static class DynamicMethodBuilder
    {public static Delegate BuildDynamicDelegate(MethodInfo methodInfo, ConstructorInfo constructorInfo = null)
        {if (methodInfo == null)throw new ArgumentNullException("methodInfo");
            List<ParameterExpression> paramExpressions = methodInfo.GetParameters().Select((p, i) =>{var name = "param" + (i + 1);return Expression.Parameter(p.ParameterType, name);
            }).ToList();
            MethodCallExpression callExpression;if (methodInfo.IsStatic)
            {//Call(params....)callExpression = Expression.Call(methodInfo, paramExpressions);
            }else{if (constructorInfo != null)
                {//Instance(params).Call(params....)List<ParameterExpression> constructorParamExpressions = constructorInfo.GetParameters().Select((p, i) =>{var name = "constparam" + (i + 1);return Expression.Parameter(p.ParameterType, name);
                    }).ToList();
                    callExpression = Expression.Call(Expression.New(constructorInfo, constructorParamExpressions), methodInfo, paramExpressions);
                    paramExpressions.InsertRange(0, constructorParamExpressions);
                }else{
                    callExpression = Expression.Call(Expression.New(methodInfo.ReflectedType), methodInfo, paramExpressions);
                }
            }return Expression.Lambda(callExpression, paramExpressions).Compile();
        } 
    }

Test:

    public class Baby
    {
        private readonly DateTime _birthDay;
        public Baby(DateTime birthDay)
        {
            _birthDay = birthDay;
        }
        public Baby()
        {
            _birthDay = DateTime.Now;
        }

        public string GetBabyInfo(string name, int sex) => $"姓名：{name} , 出生天数：{ DateTime.Now- _birthDay} ,性别 ：{(sex == 1 ? "男" : "女")}";

    }

    class Program
    {
        static void Main(string[] args)
        {
            Type targetType = Assembly.GetExecutingAssembly().GetType("ConsoleApplication1.Baby");

            MethodInfo methodInfo = targetType.GetMethod("GetBabyInfo", new[] { typeof(string), typeof(int) });
            ConstructorInfo constructor = targetType.GetConstructor(new[] { typeof(DateTime) });

            WithConstructor(methodInfo, constructor);
            WithOutConstructor(methodInfo);
            Console.ReadKey();
        }
        static void WithConstructor(MethodInfo methodInfo, ConstructorInfo constructor)
        {
            var func = (Func<DateTime, string, int, string>)DynamicMethodBuilder.BuildDynamicDelegate(methodInfo, constructor);
            Console.WriteLine(func(DateTime.Now.AddDays(-100), "糖墩儿", 1));
        }
        static void WithOutConstructor(MethodInfo methodInfo)
        {
            var func = (Func<string, int, string>)DynamicMethodBuilder.BuildDynamicDelegate(methodInfo);
            Console.WriteLine(func("糖墩儿", 1));
        }
    }

　

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