title: Worksheet get_Range throws exception
body: <p>I'm using C# to manipulate an Excel worksheet. The following two pieces of code should work the same, but one works and the other throws an exception. I wonder why.</p>
  
  <p>This works:</p>
  
  <pre><code>oRange = (Excel.Range)oSheet.get_Range("A1","F1");
  oRange.EntireColumn.AutoFit();
  </code></pre>
  
  <p>This throws an exception:</p>
  
  <pre><code>oRange = (Excel.Range)oSheet.get_Range(oSheet.Cells[1, 1],oSheet.Cells[4,4]);
  oRange.EntireColumn.AutoFit();
  </code></pre>
  
  <p>Exception:</p>
  
  <pre><code>RuntimeBinderException occurred. "object" does not contain a definition for 'get_Range'
  </code></pre>
  
  <p>The <code>oSheet</code> is instantiated as follows:</p>
  
  <pre><code>Excel.Worksheet oSheet = new Excel.Worksheet();
  </code></pre>
  
  <p>Am I supposed to instantiate both differently?</p>