Visual Studio Express 2013 for Web: Registering a new account using email instead of username

Hi, I created a new asp.net web forms site in Visual Studio Express 2013 for Web, and the default Register account page created by the software is asking the user to enter a username, password and confirm password.

How do I edit this form to ask the user to enter email instead of username?

I want the "email" textfield to be both required and validated as email, so I added a "RegularExpressionValidator" below the "RequiredFieldValidator" as follows...

<asp:TextBox runat="server" ID="UserName" CssClass="form-control" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="UserName" CssClass="text-danger" ErrorMessage="The email field is required." />
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="UserName" CssClass="text-danger" ErrorMessage="Please enter a valid email." ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*" />

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Is this the correct way? Because the "Please enter a valid email." error message is  appearing a bit too the right, as in the attached screenshot "email.jpg".

Second question, still on the register account page, even after entering a valid looking email, the two password fields and pressing "Register", there is an error message that says "User name 2@2.com is invalid, can only contain letters or digits".

In "Register.aspx.vb", there is the following code...

Public Partial Class Account_Register
    Inherits Page
    Protected Sub CreateUser_Click(sender As Object, e As EventArgs)
        Dim manager = New UserManager()
        Dim user = New ApplicationUser() With {.UserName = userName.Text}
        Dim result = manager.Create(user, Password.Text)
        If result.Succeeded Then
            IdentityHelper.SignIn(manager, user, isPersistent:=False)
            IdentityHelper.RedirectToReturnUrl(Request.QueryString("ReturnUrl"), Response)
        Else
            ErrorMessage.Text = result.Errors.FirstOrDefault()
        End If
    End Sub
End Class

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The "manager.Create" function is under "UserManagerExtensions" under "Microsoft.AspNet.Identity.Core" under "Object Browser".

What do I need to do so that I can register a new account using email address successfully?
Thanks.
email.jpg