Expression小案例

 

 

 

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;

namespace _Console
{
    public static class ExpressionTest
    {
        //Expression<Func<string, bool>> f = s => s.Length < 5;

        public static void Test()
        {
            ParameterExpression p = Expression.Parameter(typeof(string), "s");

            MemberExpression stringLength = Expression.Property(p, "Length");
            ConstantExpression five = Expression.Constant(5);

            BinaryExpression comparison = Expression.LessThan(stringLength, five);

            Expression<Func<string, bool>> lambda = Expression.Lambda<Func<string, bool>>(comparison, p);

            //end
            /*  将lambda编译为委托
            Func<string, bool> runnable = lambda.Compile();

            Console.WriteLine(runnable("kangaroo"));
            Console.WriteLine(runnable("dog"));
            */

        }
    }
}