Vb.net Vs Input - Sending An Email To User Input Email. VB

I have 2 pages, one is HTML and the other is ASPX. In the HTML I am able to get input from a user and then process a return email to them

The HTML looks like this:

<input type="text" class="input" value="e-mail" id="txtEmail" name="contactEmail" onclick="SelectAll('txtEmail');" >

and I'm using the following in the method

Dim sResponseToName As String = Request.Params("contactEmail").ToString

This part of my page works perfect as someone sends me a request I am about to direct an email to their "contactEmail"

However, in my aspx page it looks like this:

<asp:TextBox ID="contact_Email" CssClass="inputtext1" runat="server">

and the method used is:

Dim sResponseToName As String = Request.Params("contact_Email").ToString()

but no email is sent to the input email address.... If I hard code a random email instead of Request.Params("contact_Email").ToString() it works fine. But for some reason I can not get to the inputted user address.

kinda stumped, I've tried a few things but no luck. How do I get the Request.Params to work in an aspx, and do I need to add something in <asp:TextBox....> to reference it.