title: C# Linq or Lambda expression Group by Week IEnumerable list with date field
body: <p>I am trying to do a query to an <code>IEnumerable&lt;Object&gt;</code> to group by week, for example:</p>
  
  <pre><code>Project(Name, DateStart,ID)
  </code></pre>
  
  <p>I have <code>IEnumerable&lt;Project&gt;</code> and I want to do a report, grouping by week.</p>
  
  <p>For exmaple:</p>
  
  <pre><code>Week 1
   Project1  8/4/2013 ID1
   Project2  9/4/2013 ID2
  Week 2
   Project1  16/4/2013 ID3
   Project2  18/4/2013 ID5
  Week 3
   Project1  24/4/2013 ID7
   Project2  26/4/2013 ID8
  </code></pre>
  
  <p>Please if someone can give me a hand I really appreciate it! I was trying to do a lambda expression but without success.</p>
  
  <p>Thanks!</p>