返回泛型参数的基础类型的扩展方法

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

public static class ListExtensions
{
    public static string ToStringList<T>(this List<T> list)
    {
        return string.Join(", ", list.Select(item => item?.ToString() ?? ""));
    }
}

class Program
{
    static void Main()
    {
        List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
        Console.WriteLine(numbers.ToStringList()); // 输出: 1, 2, 3, 4, 5
    }
}

using System;
using System.Collections.Generic;
using ListExtensions; // 引入包含扩展方法的命名空间

class Program
{
    static void Main()
    {
        List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
        Console.WriteLine(numbers.ToStringList()); // 输出: 1, 2, 3, 4, 5
    }
}