title: What is WPF Application Service
body: <p>I am developing a MVVM WPF application. I can tell you the code looks cleaner but some menial tasks have become a big trouble for me.</p>
  
  <p>A good example is to show OpenFileDialog or heck even a MessageBox from the ModelViewer class. I know how to use the RelayCommand but I cannot make OpenFileDialog show. I read in the SO that it would require application service. What is application service?</p>
  
  <p>I cannot find any tutorial on this. Can someone explain it to me with some example as well? I know it is something related to interfaces...</p>