using System;
using System.Linq.Expressions;
class Program
{
    static void Main()
    {
        // 步驟1：定義Person類
        class Person
        {
            public string Name { get; set; }
            public int Age { get; set; }
        }
        // 步驟2：創(chuàng)建Expression參數(shù)
        ParameterExpression parameter = Expression.Parameter(typeof(Person), "p");
        // 步驟3：創(chuàng)建第一個(gè)表達(dá)式，檢查年齡是否大于等于 18
        Expression<Func<Person, bool>> ageExpression = Expression.Lambda<Func<Person, bool>>(
            Expression.GreaterThanOrEqual(
                Expression.Property(parameter, nameof(Person.Age)),
                Expression.Constant(18)
            ),
            parameter
        );
        // 步驟4：創(chuàng)建第二個(gè)表達(dá)式，檢查姓名是否為 "John"
        Expression<Func<Person, bool>> nameExpression = Expression.Lambda<Func<Person, bool>>(
            Expression.Equal(
                Expression.Property(parameter, nameof(Person.Name)),
                Expression.Constant("John")
            ),
            parameter
        );
        // 步驟5：組合表達(dá)式，要求年齡大于等于 18 且姓名為 "John"
        Expression<Func<Person, bool>> combinedExpression = Expression.Lambda<Func<Person, bool>>(
            Expression.AndAlso(ageExpression.Body, nameExpression.Body),
            parameter
        );
        // 步驟6：編譯并使用組合后的表達(dá)式
        var compiledExpression = combinedExpression.Compile();
        // 步驟7：創(chuàng)建Person對(duì)象并測(cè)試
        var person1 = new Person { Name = "John", Age = 20 };
        var person2 = new Person { Name = "Alice", Age = 25 };
        Console.WriteLine(compiledExpression(person1)); // 輸出 True
        Console.WriteLine(compiledExpression(person2)); // 輸出 False
    }
}