Email Address Validation for ASP.NET

Any script tags posted on an ASP.NET web form will cause your site to throw and unhandled exception.

You can use a asp regex validator to confirm input, just ensure you wrap your code behind method with a if(IsValid) clause in case your javascript is bypassed.If your client javascript is bypassed and script tags are posted to your asp.net form, asp.net will throw a unhandled exception.

You can use something like:

<asp:RegularExpressionValidator ID="regexEmailValid" runat="server" ValidationExpression="\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*" ControlToValidate="tbEmail" ErrorMessage="Invalid Email Format"></asp:RegularExpressionValidator>

Here is a basic email validator I just created based on Simon Johnson's idea. It just needs the extra functionality of DNS lookup being added if it is required.

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Web.UI.WebControls;using System.Text.RegularExpressions;using System.Web.UI;namespace CompanyName.Library.Web.Controls{    [ToolboxData("<{0}:EmailValidator runat=server></{0}:EmailValidator>")]    public class EmailValidator : BaseValidator    {        protected override bool EvaluateIsValid()        {            string val = this.GetControlValidationValue(this.ControlToValidate);            string pattern = @"^[a-z][a-z|0-9|]*([_][a-z|0-9]+)*([.][a-z|0-9]+([_][a-z|0-9]+)*)?@[a-z][a-z|0-9|]*\.([a-z][a-z|0-9]*(\.[a-z][a-z|0-9]*)?)$";            Match match = Regex.Match(val.Trim(), pattern, RegexOptions.IgnoreCase);            if (match.Success)                return true;            else                return false;        }    }}

Update: Please don't use the original Regex. Seek out a newer more complete sample.

You can use a RegularExpression validator. The ValidationExpression property has a button you can press in Visual Studio's property's panel that gets lists a lot of useful expressions. The one they use for email addresses is:

\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*