上接《只要十步 ， 你就可以应用表达式树来优化动态调用（一）》
第六步 ， 将静态方法换为表达式ValidateStringRequired 和 ValidateStringMinLength 两个静态方法的内部实际上只包含一个判断三目表达式 ， 而且在 C# 中 ， 可以将 Lambda 方法赋值个一个表达式 。
因此 ， 我们可以直接将 ValidateStringRequired 和 ValidateStringMinLength 改换为表达式 ， 这样就不需要反射来获取静态方法再去构建表达式了 。
using System;using System.Collections.Generic;using System.ComponentModel.DataAnnotations;using System.Diagnostics;using System.Linq;using System.Linq.Expressions;using System.Reflection;using FluentAssertions;using NUnit.Framework;// ReSharper disable InvalidXmlDocCommentnamespace Newbe.ExpressionsTests{////// Static Method to Expression///public class X03PropertyValidationTest06{private const int Count = 10_000;private static Func _func;[SetUp]public void Init(){try{var finalExpression = CreateCore();_func = finalExpression.Compile();Expression> CreateCore(){// exp for inputvar inputExp = Expression.Parameter(typeof(CreateClaptrapInput), "input");// exp for outputvar resultExp = Expression.Variable(typeof(ValidateResult), "result");// exp for return statementvar returnLabel = Expression.Label(typeof(ValidateResult));var innerExps = new List {CreateDefaultResult()};var stringProps = typeof(CreateClaptrapInput).GetProperties().Where(x => x.PropertyType == typeof(string));foreach (var propertyInfo in stringProps){if (propertyInfo.GetCustomAttribute() != null){innerExps.Add(CreateValidateStringRequiredExpression(propertyInfo));}var minlengthAttribute = propertyInfo.GetCustomAttribute();if (minlengthAttribute != null){innerExps.Add(CreateValidateStringMinLengthExpression(propertyInfo, minlengthAttribute.Length));}}innerExps.Add(Expression.Label(returnLabel, resultExp));// build whole blockvar body = Expression.Block(new[] {resultExp},innerExps);// build lambda from bodyvar final = Expression.Lambda>(body,inputExp);return final;Expression CreateDefaultResult(){var okMethod = typeof(ValidateResult).GetMethod(nameof(ValidateResult.Ok));Debug.Assert(okMethod != null, nameof(okMethod) + " != null");var methodCallExpression = Expression.Call(okMethod);var re = Expression.Assign(resultExp, methodCallExpression);/*** final as:* result = ValidateResult.Ok()*/return re;}Expression CreateValidateStringRequiredExpression(PropertyInfo propertyInfo){var isOkProperty = typeof(ValidateResult).GetProperty(nameof(ValidateResult.IsOk));Debug.Assert(isOkProperty != null, nameof(isOkProperty) + " != null");var namePropExp = Expression.Property(inputExp, propertyInfo);var nameNameExp = Expression.Constant(propertyInfo.Name);var requiredMethodExp = Expression.Invoke(ValidateStringRequiredExp, nameNameExp, namePropExp);var assignExp = Expression.Assign(resultExp, requiredMethodExp);var resultIsOkPropertyExp = Expression.Property(resultExp, isOkProperty);var conditionExp = Expression.IsFalse(resultIsOkPropertyExp);var ifThenExp =Expression.IfThen(conditionExp,Expression.Return(returnLabel, resultExp));var re = Expression.Block(new[] {resultExp},assignExp,ifThenExp);return re;}Expression CreateValidateStringMinLengthExpression(PropertyInfo propertyInfo,int minlengthAttributeLength){var isOkProperty = typeof(ValidateResult).GetProperty(nameof(ValidateResult.IsOk));Debug.Assert(isOkProperty != null, nameof(isOkProperty) + " != null");var namePropExp = Expression.Property(inputExp, propertyInfo);var nameNameExp = Expression.Constant(propertyInfo.Name);var requiredMethodExp = Expression.Invoke(ValidateStringMinLengthExp,nameNameExp,namePropExp,Expression.Constant(minlengthAttributeLength));var assignExp = Expression.Assign(resultExp, requiredMethodExp);var resultIsOkPropertyExp = Expression.Property(resultExp, isOkProperty);var conditionExp = Expression.IsFalse(resultIsOkPropertyExp);var ifThenExp =Expression.IfThen(conditionExp,Expression.Return(returnLabel, resultExp));var re = Expression.Block(new[] {resultExp},assignExp,ifThenExp);return re;}}}catch (Exception e){Console.WriteLine(e);throw;}}[Test]public void Run(){// see code in demo repo}private static readonly Expression