how to image verification in asp.net

[Vadivel Kumar]

I'm writing a data input page, which will be used by the users to input
their information. I recently heard that lot of automated programs which use
this page to send junk information into the database. And, the remedy is to
have a image verification while adding the data into the database. I know
there are namespaces in ASP.NET to write image into the browser. Now, what i
want to know is how to show alpha-numeric letters randomnly in the page.

I just need some more information, which could be straight forward as far as
the random generation of alpa-numeric generation and the background pattern
of the image.

Thanks in Advance
Vadivel Kumar