System windows forms control validating
When the user enters data in the controls which fails validation, a blinking error image is displayed on the form next to the control and the error message is displayed as a tooltip to the error image.
You can display multiple error indications on a form at the same time using the same Error Provider control.
You can also display errors that occur in Data Sets.
For example, calling Validate Children(Validation Constraints. Causes Validation property set to true in order for its Control. Validate Children(Validation Constraints), and not when the user shifts focus from the control.Select control you want to assign validation to and change its Validator1 property to choose desired validation type.In previous example you’ve seen required field validator.Invoking the Set Error method of the Error Provider control displays an error indicator image next to the control specified as the first argument to the the Set Error method.The string specified in the second argument in the function invocation is displayed as the tooltip when the mouse is moved over the Error indicator.