VS 2012 Need advice for dropdownlist control

Hello: I recently made the move from visual studio 2005 to 2012. I have a new assignment at work to create a web app.

I have a form that needs to have a dropdown on it. The user will look to see if there's a value in the dropdown that they want.
this dropdown is bound to values in my sql db.

If they don't see the value they need, they need to add it. I have recently learned that this is not possible to do using the dropdownlist control.

I wanted to come on this forum to get ideas of ways that people incorporate work-arounds for this issue.

It's tough to decide which way to go so hoping to get some ideas and pros and cons of each. e.g.
I've heard of adding a text box control directly under the dropdownlist. Do you think this is the most common approach?

Thanks,
Proctor