Programmatically create a host-named site collection

In addition to using the Windows PowerShell to create host-named sites, you can use the SharePoint Server 2010 object model. The following code sample creates the host-named site collection with the URL http://host.header.site.url in the SharePoint Server 2010 Web application with the URL http://servername:

SPWebApplication webApp = SPWebApplication.Lookup(new

Uri("http://servername"));

SPSiteCollection sites = webApp.Sites;

SPSite Site = null;

Site = sites.Add("http://hoster.contoso.com", "Site_Title",

"Site_Description", 1033, "STS#0", "contoso\owner",

"Owner_Display_Name", "Owner_Email", "contoso\secondaryowner,

"Secondary_Owner_Display_Name", "Secondary_Owner_Email", true);

SharePoint Server 2010 ships with a set of Web services for various user and administrative tasks. One of these administrative tasks is creating a new site collection. The CreateSite Web service method does not support the creation of host-named site collections. A workaround for this issue is to write a Web service that wraps the API sample code.

Ref: http://technet.microsoft.com/en-us/library/cc424952.aspx#section4