c#中的多线程/并行处理

我有4个任务要完成使用多线程的概念。我有4个服务员。

如何分配空闲的女服务员来处理其中一项任务?

-I不断得到重复的数据(例如:4线程做类似的任务)-如果我使用锁，它锁定1个线程做4个任务，这不是我想要的

我代码:

 private void MTDemo()
        {
                String threadName = Thread.CurrentThread.Name;
                while (true)
                {
                    int numWaitingCustomer = 0;
                    Int32.TryParse(textBox1.Text, out numWaitingCustomer);
                    if (numWaitingCustomer > 0)
                    {
                        String takeOrderString = String.Format("Take order {0},{1}", threadName, numWaitingCustomer);
                        String serveMeal = String.Format("Serve meal {0},{1}",threadName, numWaitingCustomer);
                        String billCustomer = String.Format("Bill Customer {0},{1}", threadName, numWaitingCustomer);
                        String cleanTable = String.Format("Clean Table {0},{1}", threadName, numWaitingCustomer);
                        OutputMessage1(takeOrderString); Thread.Sleep(500);
                        OutputMessage1(serveMeal); Thread.Sleep(500);
                        OutputMessage1(billCustomer); Thread.Sleep(500);
                        OutputMessage1(cleanTable); Thread.Sleep(500);
                        numWaitingCustomer--;
                        SetControlPropertyValue(textBox1, "text", numWaitingCustomer.ToString());
                    }
                }
            }

for(int i = threadNumber; i < taskList.length-threadNumber; i = i*totalThreads+ThreadNumber) {
    ...
}