I have read all the other posts relating to this and nothing has help me to date.

I have created a very basic User Control for my Umbraco v 4.7.0 installation.

Page_Load Events fire fine but the button click event is not handled in the OnClick server side event. 

Request.Form["__EVENTTARGET"] is returning null.

Is this a bug in 4.7? I have developed simple control in 4.5.2 with no isues at all

RegisterForCamp.ascx

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="RegisterForCamp.ascx.cs" Inherits="umbraco_controls.usercontrols.RegisterForCamp" %>

<form id="RegisterForCampForm" runat="server">
    <asp:Literal ID="litMessage" runat="server" />
    <asp:Button ID="btnRegister" runat="server" Text="Register" onclick="btnRegister_Click" />
</form>

RegisterForCamp.ascx.cs

namespace umbraco_controls.usercontrols
{
    public partial class RegisterForCamp : System.Web.UI.UserControl
    {

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                litMessage.Text = "Not a postback - works";
            }
            else
            {
                litMessage.Text = "Is a postback - works";
            }
        }

        protected void btnRegister_Click(object sender, EventArgs e)
        {
            litMessage.Text = "Button click - fails";
        }
    }
}