static void Main(string[] args)
{
Mahasiswa mhs1 = new Mahasiswa();
mhs1.Nim = "1234";
mhs1.NamaMahasiswa = "Erick";
Mahasiswa mhs2 = new Mahasiswa();
mhs1.Nim = "1235";
mhs1.NamaMahasiswa = "Wely";
Dosen dosen1 = new Dosen();
mhs1.Nik = "0043";
mhs1.NamaDosen = "Jhono";
Dosen dosen2 = new Dosen();
mhs1.Nik = "0045";
mhs1.NamaDosen = "Jhoni";
ArrayList list = new ArrayList();
list.Add(mhs1);
list.Add(mhs2);
list.Add(dosen1);
list.Add(dosen2);
Mahasiswa mhs = (Mahasiswa)list[1];
Console.WriteLine("{0}, {1}", mhs.Nim, mhs.NamaMahasiswa);
Dosen dosen = (Dosen)list[2];
Console.WriteLine("{0}, {1}", dosen.Nik, dosen.NamaDosen);
Console.ReadKey();
}