Why my button click handler in codebehind is not c

I have a Hello World MVC3 Project. I added codebehind, when I double-click on button in design time, it created the handler. It compiled and run. But when clicking on button at run-time handler is not called when setting debug point in handler. Why ?

<%@ Page Language="C#" AutoEventWireup="True"  Inherits="Index"  CodeBehind="~/Views/Home/Index.aspx.cs"%>

<!DOCTYPE html>

<html>
<head runat="server">
    <title>Index</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Panel ID="Panel1" runat="server">
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />
        </asp:Panel>
    </div>
    </form>
</body>
</html>

code behind

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI.WebControls;


public partial class Index : System.Web.Mvc.ViewPage<dynamic>
    {


        private string s = "";

        protected void Page_Load(object sender, EventArgs e)
        {

        }


        protected void Button1_Click(object sender, EventArgs e)
        {
            // handler not called
            s = this.TextBox1.Text;
        }






}

Designer generated by Visual Studio

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated. 
// </auto-generated>
//------------------------------------------------------------------------------



public partial class Index {

    /// <summary>
    /// form1 control.
    /// </summary>
    /// <remarks>
    /// Auto-generated field.
    /// To modify move field declaration from designer file to code-behind file.
    /// </remarks>
    protected global::System.Web.UI.HtmlControls.HtmlForm form1;

    /// <summary>
    /// Panel1 control.
    /// </summary>
    /// <remarks>
    /// Auto-generated field.
    /// To modify move field declaration from designer file to code-behind file.
    /// </remarks>
    protected global::System.Web.UI.WebControls.Panel Panel1;

    /// <summary>
    /// TextBox1 control.
    /// </summary>
    /// <remarks>
    /// Auto-generated field.
    /// To modify move field declaration from designer file to code-behind file.
    /// </remarks>
    protected global::System.Web.UI.WebControls.TextBox TextBox1;

    /// <summary>
    /// Button1 control.
    /// </summary>
    /// <remarks>
    /// Auto-generated field.
    /// To modify move field declaration from designer file to code-behind file.
    /// </remarks>
    protected global::System.Web.UI.WebControls.Button Button1;
}