File Stream C#

using System;
using System.IO;
public class SWBuff 
{
    public static void Main(String[] args)
    {
            string logFile = "a.log";
            string fileName = "a.log";
      string textToAdd = "asdf";
            FileStream fs = new FileStream(fileName, FileMode.CreateNew, FileAccess.Write, FileShare.None);
            StreamWriter swFromFileStreamUTF8Buffer = new StreamWriter(fs, System.Text.Encoding.UTF8, 512);
            swFromFileStreamUTF8Buffer.Write(textToAdd);
            swFromFileStreamUTF8Buffer.Flush();
            swFromFileStreamUTF8Buffer.Close();
    }
}