Sort file name in folder containing alphabets and numbers

Question

I am developing a windows app using c#. I want to search a file name with highest number that contains alphabets and numbers. files are created through my app in certain folder and the file name is the name of the user whose report is saved in it.

 

If suppose today I have saved  the file of user ''Manu'' in "D:\Report" folder and tomorrow if I have to create report of same user "Manu" then the file name should "Manu_01".  then next time for same user the file name should "Manu_02".

 

How Can I do this ???

 

 

Thanks In Advance....!!! 

 

In search I got help from here :all files are ordered in descending order, I want to sort specific filename.

 

http://stackoverflow.com/questions/20486559/get-a-list-of-files-in-a-directory-in-descending-order-by-creation-date-using-c