Problem calling the pop-up window & 'variable' is not declared - html

Question

I have a question about calling the pop-up registration ..
I want to correct the error for me regarding the pop-up window in my code ..
how can I call it in the VB code correctly to send email ?
And also show me this message " variable' is not declared" in the text boxes ..
What is the problem here?
Code as follows:
VB.net Code :
Protected Sub selectbtn_Click(sender As Object, e As EventArgs)
mpe.Show()
End Sub
Protected Sub SendEmail(sender As Object, e As EventArgs)
Dim EnglishName As String = TryCast(RepeaterCourse.FindControl("lblEnglishName"), Label).Text
Dim ArabicName As String = TryCast(RepeaterCourse.FindControl("lblCourseArabicTitle"), Label).Text
Dim StartCourse As String = TryCast(RepeaterCourse.FindControl("lblStartCours"), Label).Text
Dim EndCourse As String = TryCast(RepeaterCourse.FindControl("lblEndCourse"), Label).Text
Dim Days As String = TryCast(RepeaterCourse.FindControl("lblDays"), Label).Text
Dim CityCountry As String = TryCast(RepeaterCourse.FindControl("lblCountry"), Label).Text
Dim TextName As String = TextName.text
Dim body As String = "Email: " + TextBoxEmail.Text + "<br>" + "Name: " + TextBoxEnglishName.Text + "<br>" + "Country: " + DropDownListCountry.SelectedItem.ToString + "<br>" + "City: " + TextBoxCityName.Text + "<br>" + "Phone: " + TextBoxPhone.Text + "<br>" + "Category: " + DropDownListCategory.SelectedValue + "<br>" + "<br>" + "<br>" + "Message: " + TextComment.Text + "<br>" + hfEnglishName.Value
Dim mail As New System.Net.Mail.MailMessage()
mail.[To].Add("noor#gmail.com")
mail.Bcc.Add("noor#gmail.com")
mail.From = New MailAddress("noor#gmail.com")
mail.Subject = "From Inhouse Training ....By "
mail.Body = body
mail.IsBodyHtml = True
Dim smtp As New SmtpClient("relay-hosting.secureserver.net")
smtp.EnableSsl = False
smtp.UseDefaultCredentials = True
smtp.Send(mail)
LabelMSG.Text = "Sent Successfully"
ClearFields()
End Sub
<div id ="container">
<asp:UpdatePanel runat="server" id="UpdatePanel2" updatemode="Conditional">
<ContentTemplate>
<div class="row">
<div class="container">
<div style="text-align: center;margin-bottom: 10px;font-size: 16px;color: brown;"><asp:Label ID="lblmsg" Text="Registration Successful" runat="server" Visible="false" ></asp:Label></div>
<script type="text/javascript">
function HideLabel() {
var seconds = 5;
setTimeout(function () {
document.getElementById("<%=lblmsg.ClientID%>").style.display = "none";
}, seconds * 1000);
};
</script>
<div class="courses-listing clearfix" style="margin-bottom:30px;">
<asp:Repeater ID="RepeaterCourse" runat="server">
<ItemTemplate>
<div class="col-xs-12 col-sm-6 col-md-4 column threecol">
<div class="course-preview premium-course">
<div class="course-image">
<asp:Label ID="CourseLogo" runat="server" Text='<%# Eval("CourseLogo")%>'></asp:Label>
<%-- <div class="course-price product-price">
<div class="price-text"><span class="amount">$128</span></div>
<div class="corner-wrap">
<div class="corner"></div>
<div class="corner-background"></div>
</div>
</div>--%>
<div class="course-meta">
<header class="course-header">
<h5 class="nomargin"><asp:Label ID="lblEnglishName" runat="server" Text='<%# Eval("EnglishName")%>'></asp:Label></h5>
<br />
<%-- <span style="color: #777; font-size: 0.9em;">innovative tool to streamline the instructional design process.</span> <br />--%>
<h5 class="Arabic-Name"><asp:Label ID="lblCourseArabicTitle" runat="server" data-class="hide" Text='<%# Eval("ArabicName")%>'></asp:Label></h5>
<br />
<p class="author">
<asp:Label ID="lblStartCourse" data-class="hide" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "StartCourse", "{0:dd MMM}")%>'></asp:Label> -
<asp:Label ID="lblEndCourse" runat="server" data-class="hide" Text='<%# DataBinder.Eval(Container.DataItem, "EndCourse" , "{0:dd MMM yyyy}")%>'></asp:Label>
| <asp:Label ID="lblDays" runat="server" data-class="hide" Text='<%# Eval("Days")%>'></asp:Label> Days </p>
<asp:Label ID="lblCountry" data-class="hide" runat="server" Text='<%# Eval("CityCountry")%>'></asp:Label>
</header>
<br />
<div class="course-footer clearfix">
<%-- <asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="false" OnClick="SavePDF" CommandArgument='<%# Eval("BrochoreLink")%>' class="sim-button button14" style="line-height: 20px; color:white;">Download Brochore</asp:LinkButton>--%>
<asp:Button ID="selectbtn" UseSubmitBehavior="false" runat="server" Text="Register" OnClick="selectbtn_Click1" class="sim-button button14" style="line-height: 20px; color:white;"></asp:Button>
<%-- <asp:LinkButton ID="SelectGo" runat="server" Text="Select" ItemStyle-Width="100" CommandName="Select" class="sim-button button14" style="line-height: 20px; color:white;">Register</asp:LinkButton>--%>
<a class="sim-button button14" style="line-height: 20px; color:white;" href='/Brochures/<%# Eval("BrochoreLink")%>' target="_blank" ><span>Download Brochore</span></a>
<%-- <a class="sim-button button14" style="line-height: 20px; color:white;" href="http://store.cglobalc.com/?page_id=1191"><span></span>Register</a>--%>
<a class="sim-button button14" style="line-height: 20px; color:white;" href="InHouseTraining.aspx" target="_blank"><span>Run This Course In-House</span></a>
</div>
</div>
</div>
</div>
<asp:LinkButton Text="" ID="lnkFake" runat="server" />
<cc1:ModalPopupExtender ID="mpe" runat="server" PopupControlID="pnlPopup" TargetControlID="lnkFake"
CancelControlID="btnClose" BackgroundCssClass="modalBackground" >
</cc1:ModalPopupExtender>
<asp:Panel ID="pnlPopup" runat="server" Class="modalPopup" Style="display: none">
<div class="footer" align="right" style="float: right;">
<asp:Button ID="btnClose" runat="server" UseSubmitBehavior="false" Text="x" Style="margin: 2px;
font-size: 22px; color: white; background: none; border: none; border-color: none;
border-radius: 0px;" />
</div>
<div class="login">
<div class="login-header">
<p style="font-size: 30px; font-family: 'Lato', sans-serif; display: block; border-bottom: 1px solid rgba(255, 255, 255, 0.3);
margin: 0 0 0.1em 0; padding-bottom: 20px;">
CONTACT US
</p>
<p style="font-family: 'Lato', sans-serif; font-size: 1.25em; margin: 1em 0 0.4em 0;">
Fill out the form below to complete register!</p>
</div>
<div class="login-form">
<p class="left">
<asp:Label ID="Label1" runat="server" Text="Full Name" CssClass="login-label"></asp:Label>
<asp:TextBox ID="TextBoxName" runat="server" placeholder="Your Name" class="input"></asp:TextBox>
<br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" ValidationGroup="Register"
runat="server" ErrorMessage="*" ControlToValidate="TextBoxName" Forecolor="red"></asp:RequiredFieldValidator>
<%--<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server"
ControlToValidate="TextBoxName" ErrorMessage="Only character"
ValidationExpression="[a-zA-Z]+" Display="dynamic" Forecolor="red" Font-Size ="Small"></asp:RegularExpressionValidator>--%>
</p>
<p style="float: right;">
<asp:Label ID="Label2" runat="server" Text="Email" CssClass="login-label"></asp:Label>
<asp:TextBox ID="TextBoxEmail" runat="server" placeholder="Example#gmail.com" class="input"></asp:TextBox>
<br />
<asp:RegularExpressionValidator ID="valRegEx" ValidationGroup="Register" runat="server"
ControlToValidate="TextBoxEmail" ValidationExpression=".*#.*\..*" ErrorMessage="*Invalid Email address."
Display="dynamic" Forecolor="red" Font-Size ="Small">
</asp:RegularExpressionValidator>
<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ValidationGroup="Register"
ErrorMessage="*" ControlToValidate="TextBoxEmail"></asp:RequiredFieldValidator>
</p>
<p class="left">
<asp:Label ID="Label3" runat="server" Text="Country" CssClass="login-label"></asp:Label>
<asp:TextBox ID="TextBoxCityName" runat="server" placeholder="Your Country" class="input"></asp:TextBox>
<br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" ValidationGroup="Register"
runat="server" ErrorMessage="*" ControlToValidate="TextBoxCityName" Forecolor="red"></asp:RequiredFieldValidator>
<%--<asp:RegularExpressionValidator ID="RegularExpressionValidator2" runat="server"
ControlToValidate="TextBoxCityName" ErrorMessage="Only character"
ValidationExpression="[a-zA-Z]+" Display="dynamic" Forecolor="red" Font-Size ="Small"></asp:RegularExpressionValidator>--%>
</p>
<p style="float: right;">
<asp:Label ID="Label4" runat="server" Text="Phone Number" CssClass="login-label"></asp:Label>
<asp:TextBox ID="TextBoxPhone" runat="server" placeholder="Your Phone" class="input"></asp:TextBox>
<br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator4" ValidationGroup="Register"
runat="server" ErrorMessage="*" ControlToValidate="TextBoxPhone" ValidateEmptyText="true"
ValidationExpression="^([0-9\(\)\/\+ \-]*)$" Forecolor="red"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ID="RxvMobile" ValidationGroup="Register"
runat="server" ErrorMessage="just number" ControlToValidate="TextBoxPhone" ValidateEmptyText="false"
ValidationExpression="^([0-9\(\)\/\+ \-]*){5,9}$" Forecolor="red" Display="Dynamic" Font-Size ="Small"></asp:RegularExpressionValidator>
</p>
<p class="left">
<asp:Label ID="Label5" runat="server" Text="Comment" CssClass="login-label"></asp:Label>
<asp:TextBox ID="TextBoxComment" runat="server" placeholder="Notes" TextMode="MultiLine"
Rows="4" class="login-textarea"></asp:TextBox><br />
</p>
<p>
<asp:Button ID="Button1" UseSubmitBehavior="false" ValidationGroup="Register" runat="server"
Text="Register" CommandName="Select" class="btn btn-primary" OnClick="SendEmail"
Style="cursor: pointer; border-radius: 5px; box-shadow: none; margin-left: auto;
margin-right: auto; display: block; vertical-align: top;" />
</p>
</div>
</div>
</asp:Panel>
</div>
</ItemTemplate>
</asp:Repeater>
</ContentTemplate>
<Triggers>
</Triggers>
</asp:UpdatePanel>
</div>
Thank you ..