title: file filter in open file dialog
body: <p>I would like to add some checks to my OpenFileDialog to show All files except .exe and .jar.</p>
  
  <pre><code>  var openFileDialog = new Microsoft.Win32.OpenFileDialog
              {
                  Title = @"Upload File",
                  Filter =
                      @"All Files|*.*|Text File (.txt)|*.txt|Word File (.docx ,.doc)|*.docx;*.doc|PDF (.pdf)|*.pdf|Spreadsheet (.xls ,.xlsx)|  *.xls ;*.xlsx|Presentation (.pptx ,.ppt)|*.pptx;*.ppt",
                  FilterIndex = 1,
                  RestoreDirectory = true
              };
  </code></pre>
  
  <p>The all files options allows All files . Not just all files of the type specified after .
  If the user selects one type , ssay .txt from the drop down , the other files are not shown. But the all files option shows ALL files including exe and jar.</p>
  
  <p>I want to implement an option where I specifiy 5 file types , like above , and the All files option simply shows all the 5 file types together  instead of ALL file types.</p>