Muti Threading In For/Foreach and DataTable example

class Program
{
      static void Main(string[] args)
      {
             Threader t = new Threader();
             List<string> lst = new List<string>();
             for (int i = 0; i < 1000; i++)
                   lst.Add("number " + i);
             t.RunThreadsWithControl(lst, 110);
             t.PrintPrintedList();        //just to oversee that all numbers got printed
            Console.WriteLine("Done");
            Console.ReadKey();
      }
}
class Threader
{
        List<bool> globalThreadsFinished;        
        public bool AllThreadsFinished
       {
            get
           {
                  foreach (bool item in globalThreadsFinished)
                       if (!item)
                           return false;
                  return true;
            }
        }
        
        List<string> printedList;
        public void PrintPrintedList()
        {
                foreach (string s in printedList)
                      Console.WriteLine(s);
        }
       
        public void RunThreadsWithControl(List<string> list, int threadsAtOneTime)
        {
               printedList = new List<string>();
               for (int i = 0; i < list.Count; i++)
               {
                      int j = i;
                      globalThreadsFinished = new List<bool>();
                      while (j < list.Count)
                     {
                              if ((i + threadsAtOneTime) >= list.Count)
                                   threadsAtOneTime = list.Count - i;
                              globalThreadsFinished.Add(false);
                              int boolIndex = globalThreadsFinished.Count - 1;
                              string value = list[j];
                              Thread t = new Thread(() => HandleSingleThread(value , boolIndex));
                              t.Start();
                              if ((j + 1) >= (i + threadsAtOneTime))
                                     break;
                              ++j;
                    }
               
                    while (!AllThreadsFinished)
                    {
                            Thread waitThread = new Thread(() => WaitThread(100));
                            waitThread.Start();
                            waitThread.Join();
                    }

                     //this is optional, just to actualy see that the app actualy waits for stops
                     Console.WriteLine("AllThreadsFinished");
                     Thread waitThread2 = new Thread(() => WaitThread(1500));
                     waitThread2.Start();
                     waitThread2.Join();
                   
                     //back to the must               
                     globalThreadsFinished.Clear();
                     i = j;
              }
        }
            
        void HandleSingleThread(string s, int boolIndex)
        {
                 if (!printedList.Contains(s))
                          printedList.Add(s);
                 for (int i = 0; i < 100; i++)
                          Console.WriteLine(s);
                 globalThreadsFinished[boolIndex] = true;
        }
       
        void WaitThread(int mls)
        {
                Thread.Sleep(mls);
        }
     }
}

remember that if HandleSingleThread is calling sub-method u should probably make them as threads too cuz otherwise the program might cross-thread with them and u wont notice, and best to do there Thread.Join().
P.S. - just to state the obvious - the lst from Main can be DataTable.Rows, and just send a DataRow or ANY enumerator (da) and handle it right in your SingleThread method

also for the protocol this works too:
class Program
{
       static void Main(string[] args)
      {
            int max = 5;
            Thread[] tArr = new Thread[max];
            for (int i = 0; i < max; i++)
            {
                  int i2 = i;
                  tArr[i] = new Thread(() => Print(i2.ToString()));
                  tArr[i].Start();
            }
            for (int i = 0; i < max; i++)
            {
                  tArr[i].Join();
            }
            Console.WriteLine("Done");
            Console.ReadKey();
      }

      static void Print(string str)
     {
           for (int i = 0; i < 10; i++)
           Console.WriteLine(str);
     }
}
if u use this it is advised to run tArr and make them all null or stuff gets slow