How to force thread to perform context switch

What is a context switch?
A context switch is an action performed by operating systems to switch from one process/thread to another.
Basically, during application execution the operating system provides a CPU time for each thread.
While thread is executed its state is loaded into CPU registers.
By the time comes to execute a new thread, current's thread data is stored back in process's stack and a new process's state is loaded into CPU registers.

You can cause context switch by calling:

C/C++

• Sleep(0);

C#

• System.Threading.Thread.Sleep(0);