C#使用比较操作符(!=、<、>、<=、>=)的字符串构造Lambda表达式树,并生成委托执行

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下面是一个把C#使用比较操作符的字符串作为参数来构造一个委托

比如我告诉一个方法,我现在要比较x,y两个值,但具体是大于,还是小于,还是其它,我用操作符的字符串来当成参数,比如传递一个">"字符串给函数,我是要比较x是否大于y,然后返回一个bool型的结果

实现代码如下:

using System;using System.Linq.Expressions;class DynamicPredicate{    public static Expression<Func<T, T, bool>>    Generate<T>(string op)    {        ParameterExpression x =            Expression.Parameter(typeof(T), "x");        ParameterExpression y =            Expression.Parameter(typeof(T), "y");        return Expression.Lambda<Func<T, T, bool>>               (                   (op.Equals(">")) ? Expression.GreaterThan(x, y) :                   (op.Equals("<")) ? Expression.LessThan(x, y) :                   (op.Equals(">=")) ? Expression.GreaterThanOrEqual(x, y) :                   (op.Equals("<=")) ? Expression.LessThanOrEqual(x, y) :                   (op.Equals("!=")) ? Expression.NotEqual(x, y) :                   Expression.Equal(x, y),                   x, y               );    }}static void Main(){    string op = ">=";    var integerPredicate =        DynamicPredicate.Generate<int>(op).Compile();    var floatPredicate =        DynamicPredicate.Generate<float>(op).Compile();    int iA = 12, iB = 4;    Console.WriteLine("{0} {1} {2} : {3}", iA, op, iB,                      integerPredicate(iA, iB));    float fA = 867.0f, fB = 867.0f;    Console.WriteLine("{0} {1} {2} : {3}", fA, op, fB,                      floatPredicate(fA, fB));    Console.WriteLine("{0} {1} {2} : {3}", fA, ">", fB,                      DynamicPredicate.Generate<float>(">").Compile()(fA, fB));}

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