Visual Basic 2008 Recipes: A Problem-Solution Approach

9.16. Validate an Input Control

Problem

You need to alert the user of invalid input in a control, such as a TextBox.

Solution

Use the ErrorProvider component to display an error icon next to the offending control. Check for errors before allowing the user to continue.

How It Works

You can perform validation in a Windows-based application in a number of ways. One approach is to refuse any invalid character as the user presses a key by using a MaskedTextBox control, as shown in recipe 9-8. Another approach is to respond to control validation events and prevent users from changing focus from one control to another if an error exists. A less invasive approach is to simply flag the offending control in some way so that the user can review all the ...