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Validate an email address using RegularExpressionValidator in asp.net c#

RegularExpressionValidator - Validate email address
RegularExpressionValidator control determines whether an input control's entered value matches a pattern defined by a regular expression. This validation control is very useful to check predictable sequences of characters. RegularExpressionValidator mostly uses to validate email addresses, social security numbers, telephone numbers, postal (zip) codes, etc. You also need to add a RequiredFieldValidator control because RegularExpressionValidator cannot validate empty value control.

The Visual Studio and visual web developer .net IDE can auto-generate RegularExpressionValidator validation expression. It is a very useful and time-saving feature of visual studio. when validation failed RegularExpressionValidator control shows a predefined error message.

This example demonstrates how can we validate user-inputted email addresses by RegularExpressionValidator. When the user inputs the email address and presses the submit button, the RegularExpressionValidator control's validation expression checks whether the inputted email is a well-formed email address or not. If it is not a valid formatted email address then validation failed and stops form submission.
EmailValidation.aspx

<%@ Page Language="C#" %>

<!DOCTYPE html>

<script runat="server">
    protected void Button1_Click(object sender, EventArgs e)
    {
        Label1.Text = "Your email: " + TextBox1.Text.ToString();
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>asp.net RegularExpressionValidator example: how to validate email address</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:Red">RegularExpressionValidator: email</h2>
        <asp:Label 
             ID="Label1" 
             runat="server"
             Font-Bold="true"
             Font-Italic="true"
             Font-Size="Large"
             ForeColor="SeaGreen"
             >
        </asp:Label>
        <br /><br />
        <asp:Label 
             ID="Label2" 
             runat="server" 
             Text="Email"
             >
        </asp:Label>
        <asp:TextBox 
             ID="TextBox1" 
             runat="server"
             BackColor="DodgerBlue"
             ForeColor="AliceBlue"
             >
        </asp:TextBox>
        <asp:RequiredFieldValidator 
             ID="RequiredFieldValidator1"
             runat="server"
             ControlToValidate="TextBox1"
             Text="*"
             >
        </asp:RequiredFieldValidator>
        <asp:RegularExpressionValidator 
            ID="RegularExpressionValidator1"
            runat="server" 
            ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"
            ControlToValidate="TextBox1"
            ErrorMessage="Input valid email address!"
            >
        </asp:RegularExpressionValidator>
        <br /><br />
        <asp:Button 
             ID="Button1" 
             runat="server" 
             Text="Submit email"
             Font-Bold="true"
             ForeColor="DodgerBlue" 
             OnClick="Button1_Click"
             />
    </div>
    </form>
</body>
</html>
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