In a previous article, I have mentioned Using query string in ASP.NET C# (Web-Forms) but now in this article, I have explained how you can implement email validation in asp.net web-forms using regularexpressionvalidator with a simple example. Here are the steps to Validate email address in web-forms.

  • Create a textbox using ASP.NET textbox control
  • Add a regularexpressionvalidator control
  • Create a regex to validate the email address, in the above control
  • Add submit button control, which verify's email on click

Step 1: Create a new project in your Visual Studio, by navigating to File-> Project -> Select "Web" from left pane and "ASP.NET web application" from right pane, Click "OK"

Select "Empty" project Template and check "Web-Forms" for "Add folders and core reference", click OK

Step 2: Create a new .aspx file, right-click on Project name -> Select "Add"-> Select "New Item" -> Select "Web-Form" from right pane, give a name "Default.aspx" and click Ok.

Step 3: Use the code below to validate email id using regex

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="EmailValidator.Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:Label  id="lblEmail" Text="Email Address:" AssociatedControlID="EmailAddress" runat ="server" />
    <asp:TextBox
        id="EmailAddress"
        Runat="server" />

    <asp:RegularExpressionValidator
        id="regEmail"
        ControlToValidate="EmailAddress"
        Text="Enter valid email id"
        ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*" 
        Runat="server" />    
    
    <p></p>
    
    <asp:Button
        id="btnSubmit"
        Text="Submit"
        Runat="server" />
    
  
        </div>
    </form>
</body>
</html>

In the above code, RegularExpressionValidator has the following properties.

  • ControlToValidate – ID of the TextBox control, which needs to be validated.
  • ValidationExpression – The Regular Expression for validating the TextBox content. In this example, the Email Address regular expression is used.
  • ErrorMessage – The Error Message to be displayed when Validation fails.

Although, we have used an asp regex validator to confirm input, just ensure you wrap your code-behind method with an if(IsValid) clause in case your javascript is bypassed.

Step 4:  Enable WebForms UnobtrusiveValidationMode, in web.config, use the below code

 <appSettings>
    <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />
  </appSettings>

Inside "<configuration>", otherwise you might get error "ASP.NET Web-Form Error "WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for 'jquery'. Please add a ScriptResourceMapping named jquery(case-sensitive)."

That's it, we are done, build your project and run it in your browser.

validate-email-address-using-egularexpressionvalidator-min.gif

In case you want to validate email using from code-behind in C#, you can do it using C# and Regex like this

string pattern = @"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z";
		
		//check first string
	   if (Regex.IsMatch(EmailId1 , pattern))
	   {	
		   //email is valid, do something
	   }

you can fine-tune it by checking MX Records also using DNSClient Nuget package. and check MX Record of email as below

// for example, examplegmail.com
// domain = gmail.com
// mail = examplegmail.com
public bool ValidateMXRecord(string domain, string mail)
{
            var lookup = new LookupClient(IPAddress.Parse("8.8.4.4"), IPAddress.Parse("8.8.8.8"));
            lookup.Timeout = TimeSpan.FromSeconds(5);
            var result = lookup.Query(domain, QueryType.MX);

            var records = result.Answers;

            if (records.Any())
            {
                return true;
            }
            else
            {
                return false;
            }
}

Hope it helps, thanks.

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