C# 泛型 Generics 创建带参对象（取代反射创建对象 优化性能）

需求：使用泛型创建有参数的对象（性能上考虑，不使用反射创建）。

使用泛型创建无参（默认）构造函数的对象可以用
where :T ,new()
new T();
来实现，但是如果构造函数带有参数怎么办呢？

于是就写了一下一段代码：
这里使用了Expression 和 LambdaExpression，目的是为了生成对应类构造函数的委托，所以第一次调用会相对慢一点，随后调用就像直接new一样快，适合多次调用情况。

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using System;using System.Linq.Expressions;using System.Reflection;namespace XXX{    /// <summary>    /// ObjectCreator class used to create object at runtime.    /// </summary>    public class ObjectCreator<T>    {        #region Singleton        private ObjectCreator() { }        public static ObjectCreator<T> Instance        {            get { return Nested.m_instance; }        }        private class Nested        {            static Nested() { }            internal static readonly ObjectCreator<T> m_instance = new ObjectCreator<T>();        }        #endregion        private ObjectActivator m_rowCreatedActivator = null;        /// <summary>        /// Constructor of delegate        /// </summary>        /// <typeparam name="T">Type</typeparam>        /// <param name="args">arguments of Constructor</param>        /// <returns>Type</returns>        private delegate T ObjectActivator(params object[] args);        public T Create(Type[] types, params object[] args)        {            if (null == m_rowCreatedActivator)            {                m_rowCreatedActivator = ObjectCreator<T>.Instance.GetActivator(typeof(T).GetConstructor(types));            }            return m_rowCreatedActivator(args);        }        /// <summary>        /// Create object type at runtime.        /// </summary>        /// <typeparam name="T">Type</typeparam>        /// <param name="ctor">ConstructorInfo of Type</param>        /// <returns>Constructor of delegate</returns>        private ObjectActivator GetActivator(ConstructorInfo ctor)        {            ParameterInfo[] paramsInfo = ctor.GetParameters();            //create a single param of type object[]            ParameterExpression param = Expression.Parameter(typeof(object[]), "args");            Expression[] argsExp = new Expression[paramsInfo.Length];            //pick each arg from the params array             //and create a typed expression of them            for (int i = 0; i < paramsInfo.Length; i++)            {                Expression index = Expression.Constant(i);                Type paramType = paramsInfo[i].ParameterType;                Expression paramAccessorExp = Expression.ArrayIndex(param, index);                Expression paramCastExp = Expression.Convert(paramAccessorExp, paramType);                argsExp[i] = paramCastExp;            }            //make a NewExpression that calls the            //ctor with the args we just created            NewExpression newExp = Expression.New(ctor, argsExp);            //create a lambda with the New            //Expression as body and our param object[] as arg            LambdaExpression lambda = Expression.Lambda(typeof(ObjectActivator), newExp, param);            //compile it            ObjectActivator compiled = (ObjectActivator)lambda.Compile();            return compiled;        }    }}