<p>I am currently trying to import a semi-colon delimited text file into a database in c# using OleDb where I don't know the type (SQL Server, Access, Oracle, MySQL, postgreSQL, etc.)  Currently I'm reading in the file as a database using the Jet text reader then creating a prepared insert statement, populating the fields, then commiting at the end.  While that works, it's slow and for millions of rows, it takes way too long.</p>

<p>So my question:  Does anybody have any other thoughts on how to best import a text file to a generic database, or comments on my approaches that will lead to a faster import?</p>

<p>I cannot use 3rd party libraries or software to do this as it is part of a larger project</p>

Your best bet is to buy an off the shelf application for doing this.
Professional Off The Shelf applications use native drivers and fine tune for each type of datasource they will hit against.  This is always under the covers so you don't see how they go about it.  For example, bulkcopy is used against SQL Server; Oracle has a Data Pump.
The problem with rolling your own is that you can either spend the money to fine tune your application to work with each of the source types you're likely to encounter OR you take a huge performance hit by using the generic ODBC / ADO / Whatever drivers.
At the end of the day, you are better off either leaving this out of your product or just dealing with the inevitable slow approach that you are forced to take.  In this case that means using single insert statements for everything.
So, how much money do you have for development resources?