Blocking a thread

Hi,

I'm new with programming and I have a question relating thread. Please look at the following example:

....
thread = new Thread(new ThreadStart(Open));
thread.Start();
....

private void Open()
{
try
{
while (true)
{
receiver = new StreamReader(client.GetStream());
input = receiver.ReadLine();
......

I noticed that the thread is paused (or blocked) until "receiver" receive data. Now my question is how to replicates this behavior?
Example:

int DoSomething()
{
int result = 0;
// do something here
return result;
}

void ThreadFunction
{
while(true)
{
// process here
int b = DoSomething() <-- i want the thread to "stop" here until there is actually something to do
// process here some more
}
}

Thanks in advance.