The data validation controls are shown in Figure 1 as they appear in the Visual Studio . To use it, you link the Required Field Validator control to another control, such as a textbox, and use it to determine if the linked control has a value entered into it or it is empty.

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Validating the information entered by users is an essential part of developing a professional Web-based user interface. NET validation controls use a combination of the benefits of traditional data validation. NET data validation controls process data validation on the Web server, but you can also optionally process data validation on the user's computer. Hence, if you configure the data validation controls to enable validation on the user's computer, the resulting HTML is browser-specific.

More precisely, the rendered HTML uses a script library called Web and implements Microsoft JScript functionality that is only supported by Microsoft Internet Explorer 4.0 and later versions.

If you choose to support validation on the user's computer, performance will increase slightly.

However, to reiterate, validation will always be performed on the Web server in order to offer validation to Web browsers that do not support the client-side scripting as well as protect against the possibility of modified validation scripts.

Shannon Horn is the co-founder and chief software architect of Web Geniuses Corporation ( Hence, many times validation was not performed in a uniform manner, complex validation was difficult to implement, and Web servers were vulnerable to validation scripts being modified by malicious users.

He is a Microsoft Certified Application Developer (MCAD), Microsoft Certified Solution Developer (MCSD) and a Microsoft Certified Trainer (MCT) who has been developing Microsoft Windows and Web-based solutions as well as training for over 12 years. Shannon lives in Glendale, AZ, and is married with two daughters and a son. Validating the information entered by users is an essential part of developing a professional Web-based user interface.NET to allocate any space on the page ahead of time to display a validation control message. NET will dynamically allocate space on the page on the fly.If you choose the Dynamic value and your validation fails, you could cause visual layout problems on pages that use HTML tables for page layout.Alternatively, if the linked control is empty, data validation will fail.You'll mostly use Required Field Validator controls in conjunction with textbox controls.Furthermore, the data validation scripts are protected inside the Web server so they are not vulnerable to malicious user modifications.