Работа с текстовым файлом

string[] data = File.ReadAllLines(@"C:\Test.txt");
string firstLine = data.First();
string[] newData = new string[data.Length - 1];
for (int i = 1; i < data.Length; i++)
     newData[i - 1] = data[i];
File.WriteAllLines(@"C:\Test.txt", newData);

private static readonly object locker = new object();
 lock (locker)
{
List<string> quotelist = File.ReadAllLines(folder).ToList();
str = quotelist[0];
quotelist.RemoveAt(0);
File.WriteAllLines(folder, quotelist.ToArray());
}

//string firstLine = data.First();

private static readonly object locker = new object();
 lock (locker)
{
List<string> quotelist = File.ReadAllLines(folder).ToList();
str = quotelist[0];
quotelist.RemoveAt(0);
File.WriteAllLines(folder, quotelist.ToArray());
quotelist.Clear();
}

private static readonly object locker = new object();
do
{
try
{
 lock (locker)
  {
  List<string> quotelist = File.ReadAllLines(folder).ToList();
  str = quotelist[0];
  quotelist.RemoveAt(0);
  File.WriteAllLines(folder, quotelist.ToArray());
  quotelist.Clear();
  }
}
  catch 
  { 
  await Task.Delay(50);
  }
}while (string.IsNullOrEmpty(str));

    class DataProvider
    {
        private Queue<string> _data = new Queue<string>();
 
        private static readonly object locker = new object();
 
        private Thread worker;
 
        private const string file = "input.txt";
 
        public DataProvider()
        {
            worker = new Thread(Work) { IsBackground = true };
            worker.Start();
        }
 
        private void Work()
        {
            while (true)
            {
                if (File.Exists(file))
                {
                    string[] lines = File.ReadAllLines(file);
 
                    lock (locker)
                    {
                        foreach (var line in lines)
                            _data.Enqueue(line);
                    }
 
                    File.Delete(file);
                }
                Thread.Sleep(1000);
            }
        }
 
        public string GetData()
        {
            lock (locker)
            {
                if (_data.Count > 0)
                    return _data.Dequeue();
                else
                    return null;
            }
        }
    }

private static readonly object locker = new object();
do
{
try
{
 lock (locker)
  {
  List<string> quotelist = File.ReadAllLines(folder).ToList();
  str = quotelist[0];
  quotelist.RemoveAt(0);
  File.WriteAllLines(folder, quotelist.ToArray());
  quotelist.Clear();
  }
}
  catch 
  { 
  await Task.Delay(50);
  }
}while (string.IsNullOrEmpty(str));

str = dataProvider.GetData();