public static bool CreateVdir(string vdir, string phydir)  
{  
ServerManager serverManager = new ServerManager();  
Site mySite = serverManager.Sites["Default Web Site"];  
mySite.Applications.Add("/" + vdir, phydir); serverManager.CommitChanges();  
return true;  
} 

Site mySite = iisManager.Sites.Add("test", "http", "*:80:" + WebName + ".intranet." + TLD, @"c:\Webs\" + WebName); 

public static void CreateAppPool( string appPoolName)  
{  
try {  
ServerManager serverManager = new ServerManager();  
serverManager.ApplicationPools.Add(appPoolName);  
ApplicationPool apppool = serverManager.ApplicationPools[appPoolName];  
apppool.ManagedPipelineMode = ManagedPipelineMode.Classic;  
serverManager.CommitChanges();  
apppool.Recycle(); }  
catch { }  
} 

public static void AssignVDirToAppPool(string vdir, string appPoolName)  
{  
try  
{  
ServerManager serverManager = new ServerManager();  
Site site = serverManager.Sites["Default Web Site"];  
site.Applications["/" + vdir].ApplicationPoolName = appPoolName;  
serverManager.CommitChanges();  
}  
catch { }  
} 

public static bool DeleteVdir(string vDirName)  
{  
try  
{  
ServerManager serverManager = new ServerManager();  
Site mySite = serverManager.Sites["Default Web Site"];  
Microsoft.Web.Administration.Application application = mySite.Applications["/" + vDirName];  
mySite.Applications.Remove(application);  
serverManager.CommitChanges();  
return true;  
}  
catch {  
return false; 
}  
}