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 swFromFileTrueUTF8 = new StreamWriter(fileName, true,System.Text.Encoding.UTF8);
            swFromFileTrueUTF8.Write(textToAdd);
            swFromFileTrueUTF8.Flush();
            swFromFileTrueUTF8.Close();
    }
}