How to block specific website through vb.net web application

Hi,

How to block a website in vb.net web application without using a localhost ip (127.0.0.1) & proxy server ip address.

Requirement is when am running my application, specific site should get blocked  while the application is in running status. Application shouldn't communicate with that specific website.

The code given below doesn't works for me. When running this code it's hitting the specific site.

JavaScript
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In this JavaScript sample am just creating one function and calling this function from another function.
----------------------

<script type="text/javascript" language="javascript">

function BlockUrl() {

            var path = "C:\Windows\System32\drivers\etc\hosts";
            var sw = new StreamWriter(path, True);
            var sitetoblock = vbLf & " 127.0.0.1 xyz.com";
            sw.Write(sitetoblock);
            sw.Close();
    }

function Open() {

    BlockUrl();

}


Vb.Net
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In this vb.net sample am just blocking in Page_Load method itself. But i just want to block site, creating one method and calling that method from another.    
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Imports System.Collections.Generic
Imports System.Linq
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.IO

Namespace Sample1

    Public Partial Class _Default
        Inherits System.Web.UI.Page

        Protected Sub Page_Load(sender As Object, e As EventArgs)

            Dim path As [String] = "C:\Windows\System32\drivers\etc\hosts"
            Dim sw As New StreamWriter(path, True)
            Dim sitetoblock As [String] = vbLf & " 127.0.0.1 xyz.com"
            sw.Write(sitetoblock)
            sw.Close()

        End Sub
    End Class
End Namespace

Pls let me know is there any other way to blocking a website using vb.net web application.