title: LINQ Lambda Join Error - cannot be inferred from the usage
body: <p>I had troubles joining two DbSets and continued to receive the "cannot be inferred error". I struggled to find a solution so I thought I would share my simple answer.  There are several great posts from Jon Skeet and others but most of the answers were over my head. </p>
  
  <p>Here is the code that was causing me trouble:</p>
  
  <pre><code>using(var db = new SomeDataContext())
      {
      db.DemandData
          .Where(demand=&gt; demand.ID == SearchID)
          .Join(db.CUST_ORDER_LINE,
              supply=&gt; new { supply.LINE, supply.SALES_ORDER_ID },
              demand=&gt; new { demand.LINE_NO, demand.CUST_ORDER_ID },
              (supply, demand) =&gt; new { custOrderLineReturn = demand })
          .Select(s =&gt; s.custOrderLineReturn )
          .ToList();
      }
  </code></pre>