Generating histogram of an image

Question

Hi,

 

I have made a very simple image processing project in C# . All I have in the form is a picture box and a button. 

 

The functionality is-  on click of the button, a histogram should be generated of the picture in the picture box.

 

Can anyone tell me what code should I exactly include in the button? I am a beginner so if anyone can help me out, I'll be very grateful.