多线程锁2线程没有显示任何内容

Question

我刚刚学习多线程，现在我正在尝试锁定功能，我在这里的代码中尝试的是每2秒显示myText，但在控制台中它没有显示任何内容。

class Program
{
    string Text = "";
    long Counter = 0;
    string Source = "abc def ghi";

    static void Main(string[] args)
    {
        ThreadStart testThread1Start = new ThreadStart(new Program().WriteThread);
        ThreadStart testThread2Start = new ThreadStart(new Program().ReadThread);

        Thread[] testThread = new Thread[2];
        testThread[0] = new Thread(testThread1Start);
        testThread[1] = new Thread(testThread2Start);

        foreach (Thread myThread in testThread)
        {
            myThread.Start();
        }

        Console.ReadLine();
    }

    public void WriteThread()
    {
        while (true)
        {
            Thread.Sleep(1000);
            if (Source != null)
            {
                lock(this)
                {
                    Text = Source;
                    Counter = Counter + 1;
                }
            }
        }
    }

    public void ReadThread()
    {
        long myCounter = 0;
        string myText = "";
        while (true)
        {
            Thread.Sleep(1000);
            if (myCounter < Counter)
            {
                lock (this)
                {
                    myText = Text;
                    Console.WriteLine(myText);
                }
            }
        }
    }
}

ReadThread中的计数器始终为0，为什么会这样？它仍然锁定或什么？