C# select file from directory path

In a C# 2008/2010 desktop application, I need to be able to allow users the ability
to select a file they need to work with. There needs to be a default directory path. However I need to be able to allow users the ability to select files from whatever directory path they have access to.

Thus can you tell me. show me code, and/or point me to a url I can use as a reference to accomplish my goal?