When adding a .dll file in ArcMap, a "Cannot add an object" error is returned

Description

When working with COM custom components in ArcMap, adding .dll files manually to the component library through the ‘Add from File’ button on the Customize dialog box in ArcMap may result in the following error:

"Cannot add an object."

Note:
This is a generic error message and may occur under a number of circumstances.

Cause

The .dll file was selected instead of the .tlb file.

Solution or Workaround