title: Operator '==' cannot be applied to operands of type 'System.DBNull' and 'Int'
body: <p>I am receiving this error when trying to establish a connection with an Excel document to change the colour of all rows that have no fill.</p>
  
  <p>I have read the error log and it states that my error is at the following section of code:</p>
  
  <pre><code>try
  {
      foreach (Excel.Range row in rows)
      {
          if (row.Cells.EntireRow.Interior.ColorIndex == -4142) //error is Here
          {
              row.Interior.Color = System.Drawing.Color.Red;
          }
      }
      workbook.Save();
      workbook.Close();
  }
  catch (Exception ex)
  {
      MessageBox.Show(ex.ToString());
  }
  
  Marshal.ReleaseComObject(workbook);
  Marshal.ReleaseComObject(worksheet);
  Marshal.ReleaseComObject(application);
  </code></pre>
  
  <p>Does anyone know what is causing this error and if so how to resolve it?</p>