How to get ASP.NET control string property to display suggested list in designer dropdown?

How can I add a string property to my ASP.NET custom control that will result in the designer (either in HTML view or wysiwyg view) providing auto-complete by providing a list of some 30 suggested strings, while allowing for custom strings to be input?

Right now I'm using a property of type enum to allow the user to select from a list, but the strings have to be valid enum value names, and they need to be URIs. Also, it doesn't allow for inputting of custom strings.

From stackoverflow

• Look at TypeConverter.

  You will need to override GetStandardValues and GetStandardValuesSupported. You can feed this want ever you want at runtime.