Unable to cast COM object of type 'System.__ComObject' to interface type 'mshtml.HTMLElementCollection

Question

Am trying to use mshtml to fill a form on vb.net through the webbrowser control,

Dim doc As MSH.IHTMLDocument2 = DirectCast(wbMain.Document.DomDocument, MSH.IHTMLDocument2)
Dim buttons As MSH.HTMLElementCollection = doc.getElementsByTagName("button")
Dim Inputs As MSH.HTMLElementCollection = doc.getElementsByTagName("input")

but i get the following error

Unable to cast COM object of type 'System.__ComObject' to interface type 'mshtml.HTMLElementCollection'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{3050F56B-98B5-11CF-BB82-00AA00BDCE0B}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

can anyone help me out with the possible solution?

Answer 1

Dim buttons As MSH.HTMLElementCollection

Wrong type. That should be an IHTMLElementCollection instead. Note the leading I. The MSDN page is here.

The type that is missing the I is a coclass, not an interface. Used by scripting clients when they want to create their own collection object.