How to take screenshot of window programmatically

This code snippet illustrates how to capture desktop or any window to bmp file with minimum coding programmatically. It also demonstrates a neat way to save device context (DC) to file. For one of my application, there was need to take screenshot of active window, I searched net but couldn’t find any simple and easy code to do same. There were few ones but were too easy to understand, hence thought of writing my own code and here is the outcome.