Please Follow Below Set of Steps to Redirect Non-www To www for your domain in asp.net or asp classic Web Application : -
2. Before Closing of </system.webserver> Add below code in order to redirect your domain
from xyz.com to http://www.xyz.com for all pages of your website -
<system.webServer>
<rewrite>
<rules>
<rule name="Redirect domain.com to www" patternSyntax="ECMAScript" stopProcessing="true">
<match url=".*" />
<conditions>
<add input="{HTTP_HOST}" pattern="^xyz.com$" />
</conditions>
<action type="Redirect" url="http://www.xyz.com/{R:0}" />
</rule>
</rules>
</rewrite>
</system.webServer>
3. Save web.config file and Upload it to Hosting Server
4. Now every request to xy.com will be rewritten with http://www.xyz.com