Change site master page programmatically in SharePoint

It very simple to change the site's master page to custom master page programmatically in SharePoint 2007 environment. Recently we had released a new custom master pages. The master pages are with left menu place holders and another one is without left menu.

Provided a utility to update all sub sites master page. Find the same source code below.

siteUrl=@"http://kmsnet:2020/";
using (SPSite site =new SPSite(siteUrl))
{
foreach(SPWeb web in site.AllWebs)
{
SPSecurity.RunWithElevatedPrivileges(delegate ()
{
if(web.CustomMasterUrl.ToLower().Equals(("/_catalogs/masterpage/NoLeftMenu.master").ToLower()))
{
web.CustomMasterUrl = "/_catalogs/masterpage/NewNoLeftMenu.master";
web.Update();
}
if (web.CustomMasterUrl.ToLower().Equals(("/_catalogs/masterpage/LeftMenu.master").ToLower()))
{
web.CustomMasterUrl = "/_catalogs/masterpage/NewLeftMenu.master";
web.Update();
}
});
}
}