title: Group and Sum a List<object[]>
body: <p>I have this <code>List&lt;object[]&gt;</code></p>
  
  <pre><code>List&lt;object[]&gt; olst = new List&lt;object[]&gt;();
  
  olst.Add(new object[] { "AA1", 1 });
  olst.Add(new object[] { "AA2", 1 });
  olst.Add(new object[] { "AA2", 1 });
  olst.Add(new object[] { "AA1", 1 });
  olst.Add(new object[] { "AA1", 1 });
  </code></pre>
  
  <p>From <code>olst</code>, I need to produce a new <code>List&lt;object&gt;</code> to hold this:</p>
  
  <pre><code>"AA1", 3
  "AA2", 2
  </code></pre>
  
  <p>In other words, I need to group <strong>olst[x][0]</strong> and sum up <strong>olst[x][1]</strong>.<br />
  I could use a for loop, but I was hoping someone could help me using lambda expressions and/or linq to accomplish this.</p>