Search for the existance of a local user
using System.DirectoryServices.AccountManagement;
using (var pc = new PrincipalContext(ContextType.Machine))
{
var up = UserPrincipal.FindByIdentity(pc, IdentityType.SamAccountName, "gebruiker2");
var userExists = (up != null);
if (userExists) Console.WriteLine("user exists");
else Console.WriteLine("user not found");
}