title: C# Get all words from text file starting with X
body: <p>I have a text file that looks like this:</p>
  
  <blockquote>
    <p>('STEAM_1:0:XXXXXXXX', 'User1', 'Germany', 73677, 0, 0, 105, 151, 105, '2015-09-05'),
     ('STEAM_1:0:XXXXXX', 'User2', 'Belgium', 64005, 3, 100, 161, 277, 161, '2015-11-08'),
    ('STEAM_1:0:XXXXXXX', 'User3', 'Denmark', 52226, 0, 0, 84, 146, 84, '2015-11-05'),
    ('STEAM_1:0:XXXXXXXXX', 'User4', 'Denmark', 48300, 0, 0, 98, 291, 98, '2015-09-29'),
    ('STEAM_1:0:XXXXXXXX', 'User5', 'Denmark', 47817, 4, 1000, 104, 272, 104, '2015-11-08'),</p>
  </blockquote>
  
  <p>How do I extract the "STEAM_1:0:XXXXXXX" and nothing else to a whole new file? I have 250 users.</p>
  
  <p>I'm very new to programming, but I've tried a few things, nothing has worked though.
  Any advice will be appreciated.</p>