How to add validation asp.net

In ASP.NET, you can add validation to ensure that the data entered by users meets certain criteria before it is processed. There are two main types of validation in ASP.NET:

1. Client-Side Validation: This validation is done using JavaScript on the user's browser, providing instant feedback without requiring a server round trip.
2. Server-Side Validation: This is done on the server side after data has been submitted, ensuring that even if client-side validation is bypassed, the data is checked.

Types of Validators in ASP.NET:

ASP.NET provides several built-in validation controls that can be used both client-side and server-side.

1. RequiredFieldValidator: Ensures a control is not empty.
2. RangeValidator: Ensures the value falls within a specified range.
3. RegularExpressionValidator: Validates input against a regular expression.
4. CompareValidator: Compares the value of one control to another.
5. CustomValidator: Allows you to define custom validation logic.
6. ValidationSummary: Displays a summary of all validation errors.

Example: Using ASP.NET Validation Controls

Here's an example of how to use validation controls in ASP.NET Web Forms:

 

<asp:TextBox ID="txtEmail" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator 
    ID="rfvEmail" 
    ControlToValidate="txtEmail" 
    ErrorMessage="Email is required" 
    runat="server">
</asp:RequiredFieldValidator>
<asp:RegularExpressionValidator 
    ID="revEmail" 
    ControlToValidate="txtEmail" 
    ErrorMessage="Enter a valid email" 
    ValidationExpression="^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$" 
    runat="server">
</asp:RegularExpressionValidator>

<asp:Button ID="btnSubmit" Text="Submit" runat="server" OnClick="btnSubmit_Click" />
<asp:ValidationSummary ID="ValidationSummary1" runat="server" />