title: LINQ On DataTables With Multiple Conditions
body: <p>This query just doesnt seem to be very happy.  Any ideas anyone?</p>
  
  <pre><code>var results = from a in previousQuery
                join b in dtCounties.AsEnumerable()
                on new { a.CountyCode, a.StateCode } equals new { 
                    b.Field&lt;string&gt;("COUNTYCODE"),
                    b.Field&lt;string&gt;("StateCode") 
                }
                where b.Field&lt;bool&gt;("TrueOrFalse") == true
                select new
                {
                    CountyCode = a.CountyCode,
                    TrueOrFalse= b.Field&lt;bool&gt;("TrueOrFalse"),
                    Sum= a.Sum
                };
  </code></pre>
  
  <p>The error I get is </p>
  
  <blockquote>
    <p>"Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access."</p>
  </blockquote>
  
  <p>for the 2 columns in the right hand side of the join (ie  <code>b.Field&lt;string&gt;("COUNTYCODE")</code> and <code>b.Field&lt;string&gt;("StateCode")</code>).</p>