Datagridview

My questions are about the same project but are two fold:

1. I have two datagrid controls setup they read from a table in a database.

When the application is ran however i have extra blank rows at the bottom of both grids how do i delete them.

2. Once this is done i need to be able to randomly select values from both datagrids the amount of values will vary but still i need to randomly select values.

Is this possible? i've seen a lot of code for randomly selecting rows but not randomly selecting cells.

attached is my code and as you can guess it will eventually be a playable keno game