问FileStreams的奇怪行为

EN

void WriteFiles(byte[] data)
{
    foreach (string fileName in fileNames)//fileNames is my List<string>
    {
        FileStream fs = File.Create(fileName)

        fs.Write(data, 0, data.Length);

        fs.Close();
    }
}

using System;
using System.Collections.Generic;
using System.IO;

namespace ConsoleApplication1
{
   class Program
    {
        static List<string> fileNames = new List<string>();

        static void Main()
        {
            Directory.CreateDirectory("C:\\textfiles");
            fileNames.AddRange(new string[] { "1.txt", "2.txt", "3.txt" });
            WriteFiles();
        }

        static void WriteFiles()
        {
            foreach (string fileName in fileNames)
            {
                using (StreamWriter sw = new StreamWriter(File.Create("c:\\textfiles\\" + fileName)))
                {
                    sw.Write("This is my text");
                }
            }
        }
    }
}