Help needed with simple multi-threading sample code

[Mark Huebner]

The following sample code for the lock statement is on page 112 of the
O'Reilly book "C# Essentials". Can somebody explain to me why this
recursive class definition of LockTest does not cause an infinite number of
LockTest objects to be created (i.e., until it consumes all available
memory)? I don't understand why only two threads are created.
using System;
using System.Threading;

class LockTest
{
static void Main()
{
LockTest lt = new LockTest();
Thread t = new Thread(new ThreadStart(lt.Go));
t.Start();
lt.Go();
}
void Go()
{
lock(this)
for (char c='a'; c<='z'; c++)
Console.Write(c);
}
}

[Martin Platt]

Well, lock is used for a critical section, so if a second thread tries to access the code in the locked section, it will be forced to wait until the locking thread has finished. So, with that in mind, the first thread is created, then the secodn which waits on the first, then the first finished, and the seond thread gets the lock, then a new thread is created, and waits on that thread, and so on.....

Does that help?

Martin.

"Mark Huebner" wrote:

The following sample code for the lock statement is on page 112 of the
O'Reilly book "C# Essentials". Can somebody explain to me why this
recursive class definition of LockTest does not cause an infinite number of
LockTest objects to be created (i.e., until it consumes all available
memory)? I don't understand why only two threads are created.
using System;
using System.Threading;

class LockTest
{
static void Main()
{
LockTest lt = new LockTest();
Thread t = new Thread(new ThreadStart(lt.Go));
t.Start();
lt.Go();
}
void Go()
{
lock(this)
for (char c='a'; c<='z'; c++)
Console.Write(c);
}
}

[Mohamoss]

Hi Mark
Because there is no recursive call in that, all what is done here is that
you are just creating an instance of an object in the main method of the
class. Because main is the entry point , it is run at the start of the
program AND IT RUN ONLY ONCE . Notice that the main is static function i.e.
it is a function of the class not of the class objects. What you are
expecting would happen if there were a call to main from within the main
function, which is not there.
In fact this is the model that is used in c# windows application. Where the
main from is created from within the main function of its class.
Hope that was clear

Mohamed Mahfouz
MEA Developer Support Center
ITworx on behalf of Microsoft EMEA GTSC