ASP.NET CompareValidator

Introduction

This tutorial introduces the CompareValidator control in ASP.NET. The CompareValidator is used to compare the values of two input fields, ensuring that they meet certain conditions, such as equality or inequality.

CompareValidator in ASP.NET

Syntax

The CompareValidator control can be added to an ASP.NET page and configured through both design view and code-behind. The basic syntax is as follows:

<asp:CompareValidator
    ID="CompareValidator1"
    runat="server"
    ControlToValidate="TextBox1"
    ControlToCompare="TextBox2"
    Operator="Equal"
    ErrorMessage="The values must be equal."
    Display="Dynamic" />

Example

Consider a scenario where you want to compare two password fields for equality:

<asp:TextBox ID="txtPassword" runat="server" TextMode="Password"></asp:TextBox>
<asp:TextBox ID="txtConfirmPassword" runat="server" TextMode="Password"></asp:TextBox>

<asp:CompareValidator
    ID="ComparePassword"
    runat="server"
    ControlToValidate="txtConfirmPassword"
    ControlToCompare="txtPassword"
    Operator="Equal"
    ErrorMessage="Passwords must match."
    Display="Dynamic" />

Output

The output is a dynamic validation message that appears when the compared values do not meet the specified conditions.

Explanation

• ControlToValidate: Specifies the ID of the control to validate.
• ControlToCompare: Specifies the ID of the control to compare against.
• Operator: Specifies the type of comparison (e.g., "Equal," "NotEqual," "GreaterThan," etc.).
• ErrorMessage: Specifies the error message to display if the validation fails.
• Display: Specifies when the error message should be displayed ("Static," "Dynamic," or "None").

Use

• Password Confirmation: Ensure that a password confirmation field matches the original password.
• Date Validation: Validate that an end date is not earlier than the start date.
• Numeric Validation: Compare numeric values to enforce specific relationships (greater than, less than, etc.).

Important Points

1. The ControlToValidate and ControlToCompare properties should point to valid input controls on the page.
2. Choose the appropriate Operator based on the type of comparison needed.
3. Consider using client-side validation for improved user experience.

Summary

The CompareValidator control in ASP.NET provides a convenient way to perform comparisons between input values, ensuring that they meet specific conditions. Whether validating passwords, dates, or numeric values, the CompareValidator enhances the data validation capabilities of ASP.NET web forms.