title: Microsoft.Office.Interop.Excel.WorksheetFunction does not contain all the functions in excel
body: <p>I am trying to call excel functions from C#. I can use the following code to get the excel functions:</p>
  
  <pre><code>Application app = new Application();
  WorksheetFunction functions = app.WorksheetFunction;
  var sum = functions.Sum(1, 2);
  </code></pre>
  
  <p>I can get the function like SUM from the WorksheetFunction object. But now all the functions are there, like LEFT, RIGHT, DATE etc. Can I find them somewhere else?</p>