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Expertise: Advanced
Language: Visual Basic

November 20, 2000

Passing an ActiveX Control As a Parameter

Trying to pass an ActiveX control as a parameter to a method on an external ActiveX DLL (or EXE), garners a ”Type Mismatch” error. This error is peculiar, as it does not happen on a development computer. It occurs when the component is installed on another computer.

This problem has been recognized in the MSDN knowledge base under the article titled “PRB: Passing ActiveX Control to Component Gives ‘Type Mismatch’ Error Message.” The solution proposed in the knowledge base article is to make the receiving variable type ‘object’ so that it is assigned without throwing a ‘Type Mismatch’ error. This solution does not let you sink the events of the ActiveX control in the ActiveX DLL to which the control is being passed. In order to use the ‘WithEvents’ keyword, you need to declare your variable with the correct type of information, like Private WithEvents m_tree As TreeView. A solution to this problem is to refer to the ActiveX control in your DLL using ‘References’ instead of ‘Components.’

To do this, clear the entry corresponding to the ActiveX control in the ‘Project-Components’ dialog. Then open up ‘Project-Reference’ dialog and select the same ActiveX control. Compile the DLL and install. This will eliminate the type mismatch error when the application is run.