title: Visual C#: Move multiple files with the same extensions into another directory
body: <p>guys. I've got a problem I can't solve:
  I have a 2 folders I choose with folderBrowserDialog and tons of files in source directory I need to move to the target directory. But, I have only to move files with a specific extension like .txt or any other extension I can get from textbox.
  So how can I do it?</p>