Checkbox As Boolean Conundrum?

i have a form with text boxes for username, initials, and password on.Also on this form are a few checkboxes which at the minute i simply want to save their state to SQL as true or false depending if ticked or not. The checkboxes or text boxes are not bound to anything, and are used only for creating a new record in the table.There is a gridview below these boxes showing already created records.The code im using to insert to SQL with is:

If String.IsNullOrEmpty(UsernameTb.Text) Then
MsgBox("You must enter a Username!")
Else[code].....

For some reason when i create a new record, it saves the check state as -1 for checked, and 0 for unchecked. the table columns are varchar(5) for the check boxes.Using checkboxname.checkstate doesent work either - that saves the state as 1 or 0 (as opposed to -1 and 0)On another form i made for editing existing entries, i have the same text boxes and check boxes, which are bound so they show the record details. when using that form to EDIT an entry, it saves the check box states as "True" or "False" as it should do.Im completely stumped here, because if i create a new user it then breaks the gridview showing users, because it throws up error messages about "-1 not being valid boolean" when it attempts to render each check box in a grid view. how i can make the insert save the check box state as boolean?