title: Excel C# Interop vs. Excel VBA
body: <p>I am in charge of finding bottlenecks in a Excel Add-in.  Some of the workbooks calculate extremely slowly.  I have the experience of working with VBA code, and the older versions of our product used all VBA code to execute calculations.  However, in the newer versions of the product, a lot of the calculations are being done through the add-in, which is build on top of ASP.NET C# using Excel.Interop libraries.  My question is this: Do interop libraries just run slower then code that resides directly in a workbook in the VBA?  From my experience, all projects using Excel.Interop run extremely slow on intense calculations.  If so, does anyone have any advice on speeding up Excel.Interop processes and functions?</p>
  
  <p>Thanks.</p>