Invalid Cast Exception

Hi all!

Why I can't convert the type OleDbConnection to IdbConnection
I'm using the sentence:
Ctype(<something of type OleDbConnection>, IdbConnection)

it's generates the error:
[InvalidCastException: Specified cast is not valid.]


If oledbconnection implements idbconnection, I could cast it? or not? Why?

Thanks

(I'm trying to do this cast because I'm using a dataProvider, then i set the data of my provider in the web.config file
I create the provider reading the values of web.config and one of this is the ConnectionType (it is a System.Data.OleDb.OleDbConnection in this case), but for using it in the program I always use the reference to the interface for not rewrite the code if I change the database.
When i'm trying to inizialize the connection I have this sentence

_conn = CType(_provider.ConnectionType, IdbConnection)

I dont know if this is correct but you can try it.

CType(_provider.ConnectionType, (OleDbConnection) IdbConnection)