C# format date

Question

In a C# 2008 application, I will obtain the current date by using  the statement:

DateTime.Now;

I want to read from a file that is in part of the directory path of:

mm_dd_yy. Or in other words the format is: 09_27_12. 

Thus can you tell me how to change the date obtained from datetime.now and make it look like: 09_27_12?