ASP.NET - Validators

Validators are ASP.NET server controls that are used to validate user input on a web page. They can be added to any input control on the web form, such as textboxes, dropdown lists, and checkboxes.

Validators are essential for web forms because they ensure that the data entered by the user is valid and accurate. This can help to prevent errors and inconsistencies in the data that is collected from the user.

Validators come in different types, each of which performs a specific type of validation. Some of the most common types of validators are:

• RequiredFieldValidator: This validator ensures that a user has entered a value in a required field. If the field is left blank, an error message is displayed.
• RangeValidator: This validator ensures that the value entered by the user is within a specific range of values. For example, you could use this validator to ensure that a user has entered a value between 1 and 100.
• CompareValidator: This validator compares the value entered in one control to the value entered in another control. For example, you could use this validator to ensure that the user has entered the same password in two different fields.
• RegularExpressionValidator: This validator ensures that the value entered by the user matches a specific pattern. For example, you could use this validator to ensure that the user has entered a valid email address.

To use a validator in your ASP.NET application, you must first add the appropriate validator control to the web form. You can then set properties such as the control to validate, the error message to display, and the validation type.

When the user submits the form, the validators are automatically triggered and the appropriate error messages are displayed if any of the validation checks fail. This ensures that the data collected from the user is accurate and meets the requirements of the application.