bindingsource and bindingnavigator and validation

[gacaccia]

i've got VS.NET 2005 and i'm trying to make some quick dialogs for adding,editing,deleting data from a table in a database. i've created a form and dragged the table onto the form from my datasource view. this created an object for tableadapter, dataset, bindingsource and bindingnavigator. i can open the form and see the data, along w/ add, edit and delete. however, i have no idea how to validate data. for example, i can click the "+" button to add a record and, without entering any data, immediately click the "+" button again. this results in an application error as it tries to add a blank row. how would i check for things like this?