What is a RegularExpressionValidator?

RegularExpressionValidator control is used to check a value against a regular expression. It checks whether the value of the associated input control matches the pattern of the regular expression. This Control generally used to check whether the entered phone number or email address matches a set format. A notable property of this control is the ValidationExpression property, which is used to set the validation criteria and which comes with some predefined formats.

To work with a RegularExpressionValidator control; Drag a TextBox and a Command Button from the ToolBox. Our intention is to check for the format of an email address and display an error message if the input format is not correct. An example of a correctly formated inpput would be "xyz@programmersheaven.com". To implement format definition. In the properties window of the Regularexpression click on the ellipse button for ValidationExpression and select Internet E-mail Address from the pop-up window. When you run the program and enter a value not in the format of abc@xyz.com the error message is displayed.

Written by Sandeep Mogulla, Webmaster at www.startvbdotnet.com

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