title: Unable to cast COM object of type 'Microsoft.Office.Interop.Excel.WorksheetClass'
body: <p>I'm trying to create and save a new excel document in C# from a bunch of aggregate data.  Right now, I'm just trying to get the basics working as far as editing the table cells, etc.  Here's me just trying to set the contents of one cell:</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.IO;
  using System.Linq;
  using System.Text;
  using System.Threading.Tasks;
  
  using Microsoft.Office.Interop.Excel;
  
  namespace DebugReport
  {
      class MonumentDebugReport
      {
          static void Main(string[] args)
          {    
              Worksheet spreadsheet = new Worksheet();
  
              spreadsheet.Cells[0, 0] = "stuff";
         }
      }
  }
  </code></pre>
  
  <p>This returns:</p>
  
  <p>Unable to cast COM object of type 'Microsoft.Office.Interop.Excel.WorksheetClass' to interface type 'Microsoft.Office.Interop.Excel._Worksheet'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{000208D8-0000-0000-C000-000000000046}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).</p>
  
  <p>on the line in which I'm setting the cell.  To me, this looks exactly like most of the examples / tutorials I've seen, and I can't find anything in the C# documentation to indicate that this wouldn't work.</p>