title: LINQ (Unable to cast object of type 'System.Double' to type 'System.String'.)
body: <p>I am facing a problem while using LINQ concept.
  below i am comparing two datatables one is filled by database another is by excel file.</p>
  
  <p>Problem is when I am apply join between two "tempdt" contains double value which promoting an error of casting object.
  I can't change return type from string to double cause it could be any data type in future as currently it is double it might be alpha numeric in future.</p>
  
  <pre><code>    var commonRows = from r1 in dt.AsEnumerable()
                               join r2 in tempdt.AsEnumerable()
                               on r1.Field&lt;string&gt;(0) equals r2.Field&lt;string&gt;(4)
                               select r2;
              if (commonRows.Any())
              {
                  abcdefgh = commonRows.Count();
                  dt123 = commonRows.CopyToDataTable();
                  // ring the ghanta of gutlu
              }
  </code></pre>
  
  <blockquote>
    <p><em>Exception: Unable to cast object of type 'System.Double' to type
    'System.String'.</em></p>
  </blockquote>