title: Linq query to with SortedList<int,list<int>>
body: <p>I am currently using Linq to retrieve a list of distinct values from my data table. I am then looping through the list and again calling a linq query to retrieve a list of values for each
  value in the first list.</p>
  
  <pre><code>_keyList = new SortedList&lt;int, List&lt;int&gt;&gt;();
  var AUGroupList = ProcessSummaryData.AsEnumerable()
                    .Select(x =&gt; x.Field&lt;int&gt;("AUGroupID"))
                    .Distinct()
                    .ToList&lt;int&gt;();
  foreach (var au in AUGroupList)
  {
      var AUList = ProcessSummaryData.AsEnumerable()
                        .Where(x =&gt; x.Field&lt;int&gt;("AUGroupID") == au)
                        .Select(x =&gt; x.Field&lt;int&gt;("ActivityUnitID"))
                        .ToList&lt;int&gt;();
      _keyList.Add(au, AUList);
  }
  </code></pre>
  
  <p>I am then adding the value to a sorted list along with the corresponding second list.
  How can I combine the above two queries into one Linq query so that I don't have to call them separately?</p>