LoadRunner C#.NET Vuser

Hi All,

Please help me how to use this function in Visual Studio LoadRunner C#.NET Vuser:

LoadRunner.WebApi web = new LoadRunner.WebApi();

web.url("newtours.demoaut.com", "URL=http://newtours.demoaut.com/");

web.submit_form("login.php", "Name=userName, Value=mercury, ENDITEM," +
                    "Name=password, Value=mercury, ENDITEM", "LAST");

I tried multiple times but system is always present incorrect page after submit form

Please help,

Thanks so much