Two Threads printing ABCD sequence one in upper and another in lower

Suppose there is a ABCD.... sequence we want to print this sequence on Two threads. One thread printing in Upper case and another in Lower case without breaking the sequences or order.

Output should look like

A--thread1
a--thread2
B--thread1
b--thread2
C--thread1
c--thread2


Solution Code
 
using System;
using System.Threading;
class Program
{
    static void Main()
    {
        Thread T1 = new Thread(new ThreadStart(Th1));
        Thread T2 = new Thread(new ThreadStart(Th2));
        T1.Start();
        T2.Start();
    }
   
    static void Th1(){
        string str ="ABCDEF"   ;
        foreach(char c in str){
            Console.WriteLine(c.ToString().ToLower());
            Thread.Sleep(1000);
        }
    }
   
    static void Th2(){
        string str ="ABCDEF"   ;
        foreach(char c in str){
            Console.WriteLine(c);
            Thread.Sleep(1000);
        }
    }
}

Output
A
a
B
b
C
c