使用linq合并三个列表

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        List<int> list1 = new List<int>() { 1, 2, 3 };
        List<int> list2 = new List<int>() { 4, 5, 6 };
        List<int> list3 = new List<int>() { 7, 8, 9 };

        var mergedList = list1.Concat(list2).Concat(list3);

        foreach (var item in mergedList)
        {
            Console.WriteLine(item);
        }
    }
}