How To Add MetaDescription And MetaKeywords Feature

I have a alreday developed web application. Now I am wishing to add MetaDescription and MetaKeywords feature. I have downloaded codes from here

****. This is my own post but now it is wondering me when I am using that code and codebehind in my project. Well here is my codes and errors.

Partial Class _Default Inherits System.Web.UI.Page Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load ' Changing title of the Page Page.Header.Title = String.Format("Header Content ({0})", DateTime.Now)

' Changing background of Page
Dim myStyle As New Style()
myStyle.BackColor = System.Drawing.Color.Red
Page.Header.StyleSheet.CreateStyleRule(myStyle, Nothing, "html")
' Creating Meta Description
Dim metaDesc As New HtmlMeta()
metaDesc.Name = "DESCRIPTION"
metaDesc.Content = "A sample of using HtmlMeta controls"
' Creating Meta Keywords
Dim metaKeywords As New HtmlMeta()
metaKeywords.Name = "KEYWORDS"
metaKeywords.Content = "HtmlMeta,Page.Header,ASP.NET"
' Adding Meta controls to HtmlHead
Dim head As HtmlHead = CType(Page.Header, HtmlHead)
head.Controls.Add(metaDesc)
head.Controls.Add(metaKeywords)
End Sub
End Class

<%@ Page Title="" Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

This is my content.
<br />This is my content.
<br />This is my content.
<br />This is my content.
<br />This is my content.
</asp:Content>

Error:

NullReferenceException was unhandled by user code
See underlined code that has error.

Is I have to add something inside web.config file or anything else?