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RegularExpressionValidator - ( ASP.NET Validation )

ASP.NET provides a series of validation controls that allow you to validate user input without writing any custom code. Among these controls, the RegularExpressionValidator control is used to check whether the user input matches a specified pattern. In this tutorial, we will discuss the RegularExpressionValidator control and its usage.

Syntax

Here is the syntax of the RegularExpressionValidator control:

<asp:RegularExpressionValidator
    ID="RegularExpressionValidator1"
    runat="server"
    ControlToValidate="TextBox1"
    ValidationExpression="expression"
    ErrorMessage="error message">
</asp:RegularExpressionValidator>
  • ID: A unique identifier for the control.
  • runat: It is a required attribute that specifies whether the control should be processed on the server or on the client.
  • ControlToValidate: The ID of the control to validate.
  • ValidationExpression: A regular expression that defines the pattern to match.
  • ErrorMessage: The error message to display if validation fails.

Example

Here's an example of the RegularExpressionValidator control:

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server"
    ControlToValidate="TextBox1"
    ValidationExpression="^\d{3}-\d{2}-\d{4}$"
    ErrorMessage="The SSN must be in the format XXX-XX-XXXX">
</asp:RegularExpressionValidator>

In the above example, the RegularExpressionValidator control is used to validate a Social Security number. The ValidationExpression property is set to a regular expression that represents the pattern for a valid SSN. The ControlToValidate property is set to the ID of the TextBox control to validate. The ErrorMessage property specifies the error message to display if validation fails.

Output

When the user enters an invalid input, the RegularExpressionValidator control displays the specified error message. If the input is valid, the form submits as normal.

Explanation

The RegularExpressionValidator control uses a regular expression to validate user input. The ValidationExpression property specifies the regular expression pattern to match. The control compares this pattern to the user input, and if there is a match, the input is considered valid. Otherwise, the control displays the specified error message.

Use

The RegularExpressionValidator control is used to validate user input that follows a specific pattern. You can use it to validate inputs such as email addresses, phone numbers, Social Security numbers, and more. It's an effective way to ensure that users enter data in the correct format, reducing the likelihood of errors or inaccuracies.

Important Points

  • The RegularExpressionValidator control is used to validate user input that follows a specific pattern.
  • It uses a regular expression to match patterns.
  • The ValidationExpression property specifies the regular expression pattern to match.
  • The ControlToValidate property specifies the control to validate.
  • The ErrorMessage property specifies the error message to display if validation fails.

Summary

In this tutorial, we discussed the RegularExpressionValidator control and its usage. We covered the syntax, example, output, explanation, use, important points, and summary of the RegularExpressionValidator control. RegularExpressionValidator is a powerful control that makes form validation easy, and helps ensure that users enter data in the right format.

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