How to validate email address format using ASP.Net RegularExpression Validator

    <asp:TextBox ID="txtEmail" runat="server"></asp:TextBox>
    <asp:RequiredFieldValidator ID="RequiredFieldValidator1" Display = "Dynamic" ControlToValidate="txtEmail"
        runat="server" ErrorMessage="Required"></asp:RequiredFieldValidator>
    <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="txtEmail"
        ErrorMessage="Invalid Email Address!" Display = "Dynamic" ValidationExpression="^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$"></asp:RegularExpressionValidator>
        <br />
    <asp:Button ID="Button1" runat="server" Text="Button" />