With Visual Studio 2010, you may receive the following compile-time error message after adding an ActiveX control to your form:
error CS1703: An assembly with the same identity 'stdole, Version=n.n.n.n, Culture=neutral, PublicKeyToken=nnnnnnnnnnnnnnnn' has already been imported. Try removing one of the duplicate references.
This can occur when multiple versions of this dll (stdole) exist on your system. Visual Studio 2010 erroneously adds multiple references to your project. Other Visual Studio versions, like 2005, 2008 and 2012, work correctly and add just one reference.
To correct the problem, remove all but one of the references to Stdole.
C#: Use the menu command View, Solution Explorer, expand the References branch, select (highlight) the extra Stdole reference(s) and hit the Delete key.
VB.NET: Use the menu command Project, projectname Properties..., then click on the References tab, select (highlight) the extra Stdole reference(s) and hit the Delete key.