简单介绍c#表达式树Expression简单类型比较demo的示例代码-木庄网络博客

本文摘自PHP中文网，作者黄舟，侵删。

下面小编就为大家带来一篇浅谈c#表达式树Expression简单类型比较demo。小编觉得挺不错的，现在就分享给大家，也给大家做个参考。一起跟随小编过来看看吧

实例如下：

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));
 
    Console.ReadLine();
  }