Sometimes it happens that we bound TextBox with BindingSource for a Numeric Column, if we try to put a non-numeric value or a very large numeric value in that TextBox, the application stuck, i.e. cannot get out from TextBox, cannot close the Form. This is because internal validation is running.
Whenever we try to get out from TextBox control or try to close the Form, validation happens and if value (provided in TextBox) is NOT a legal value for that particular column then validation fails, which causes the focus to remain in the TextBox control.
To solve this issue just set the CausesValidation property of TextBox control to False. This will stop the automatic Validation.