C# csvUtil

public class CSVUtil
    {
        private CSVUtil()
        {
        }
        //write a new file, existed file will be overwritten
        public static void WriteCSV(string filePathName,List<String[]>ls)
        {
            WriteCSV(filePathName,false,ls);
        }
        //write a file, existed file will be overwritten if append = false
        public static void WriteCSV(string filePathName,bool append, List<String[]> ls)
        {
            StreamWriter fileWriter=new StreamWriter(filePathName,append,Encoding.Default);
            foreach(String[] strArr in ls)
            {
                fileWriter.WriteLine(String.Join (“,",strArr) );
            }
            fileWriter.Flush();
            fileWriter.Close();
           
        }
        public static List<String[]> ReadCSV(string filePathName)
        {
            List<String[]> ls = new List<String[]>();
            StreamReader fileReader=new   StreamReader(filePathName); 
            string strLine="";
            while (strLine != null)
            {
                strLine = fileReader.ReadLine();
                if (strLine != null && strLine.Length>0)
                {
                    ls.Add(strLine.Split(','));
                    //Debug.WriteLine(strLine);
                }
            }
            fileReader.Close();
            return ls;
        }
       
    }