c# - Call non-registered .NET dll from Excel VBA

Question

I need to write a .NET dll that can be called directly from an Excel's VBA Module such that the dll and .xls are simply deployed in the same directory without any COM registration.

Purpose of dll is to run algorithms implemented in C.

How should I proceed? Is this possible at all?

Answer 1

You don't explain what the role of .NET would be in your scenario. You can indeed call many C libraries directly from VBA using 'Declare Function'.

If you find .NET useful, and want to call your .NET library functions as user-defined functions (UDFs) from Excel, you can use Excel-DNA. It gives you an .xll add-in library that integrates your .NET library into Excel. You'd still have to open the .xll add-in somehow - either by File -> Open, by adding it as an Excel add-in, or automatically from some VBA in your workbook. But it needs no other registration.

From the .NET library you can call the C .dll functions using P/Invoke, add categories, function and argument descriptions to integrate into the function wizard etc.

(Disclaimer: I'm the developer of Excel-DNA.)