TODO:
Have you ever wanted to change the username and password for an Application Pool using C#?
SOLUTION:
using(ServerManager serverManager = new ServerManager())
{
ApplicationPool pool = serverManager.ApplicationPools["AppPoolName"];
pool.ProcessModel.IdentityType = ProcessModelIdentityType.SpecificUser;
pool.ProcessModel.UserName = @"username";
pool.ProcessModel.Password = @"password";
serverManager.CommitChanges();
}
NOTES:
You need to add a reference to Microsoft.Web.Administration dll, located in Windows\System32\inetsrv directory