title: LINQ: Count number of true booleans in multiple columns
body: <p>I'm using LINQ to SQL to speed up delivery of a project, which it's really helping with. However I'm struggling with a few things I'm used to doing with manual SQL.</p>
  
  <p>I have a <strong>LINQ collection containing three columns, each containing a boolean value</strong> representing whether an e-mail, mobile or address is availble.</p>
  
  <p>I want to <strong>write a LINQ query to give me an count of trues for each column</strong>, so how many rows in the e-mail column are set to true (and the same for the other two columns)</p>