The lock statement does not work when there is a loop inside it?

Question

See this code:

public class multiply
{
    public Thread myThread;
    public int Counter
    {
        get;
        private set;
    }
    public string name
    {
        get;
        private set;
    }

    public void RunConsolePrint()
    {

        lock(this)
        {
        RunLockCode("lock");
        }


    }

    private void RunLockCode(string lockCode)
    {
        Console.WriteLine("Now thread "+lockCode+" " + name + " has started");
        for (int i = 1; i <= Counter; i++)
        {
            Console.WriteLine(lockCode+" "+name + ": count has reached " + i + ": total count is " + Counter);
        }
        Console.WriteLine("Thread " + lockCode + " " + name + " has finished");
    }
    public multiply(string pname, int pCounter)
    {
        name = pname;
        Counter = pCounter;
        myThread = new Thread(new ThreadStart(RunConsolePrint));
    }

}

And this is the test run code:

    static void Main(string[] args)
    {
        int counter = 50;

        multiply m2 = new multiply("Second", counter);
        multiply m1 = new multiply("First", counter);
        m1.myThread.Start();
        m2.myThread.Start();
        Console.ReadLine();
    }

I would expect that I have m2to execute from start to finish before it m1starts execution, or vice versa, due to instructions lock. But the result I found was that the lock call was the first, and the lock of the second was mixed together, i.e. something like this

Now thread lock First has started
Now thread lock Second has started
lock First: Count has reached 1: total count is 50
lock First: Count has reached 2: total count is 50
lock Second: Count has reached 1: total count is 50

What have I done wrong?

Answer 1

Each code instance is locked on a different object. The lock object must be shared between all instances - make it a static class variable.

private static object syncRoot = new object();
public void RunConsolePrint()
{
    lock(syncRoot)
    {
         RunLockCode("lock");
    }    
}