private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) { dataBase = new ProgramLogicDll.ConnectDb(); int Id = int.Parse(comboBox1.SelectedItem.ToString()); var computer = dataBase.Computers.Where(computerId => computerId.ComputerId == Id).FirstOrDefault(); textBox1.Text = computer.GraphicsCard; textBox2.Text = computer.Processor; textBox3.Text = computer.RAM.ToString(); foreach (var item in dataBase.Computers.Where(computerId => computerId.ComputerId == Id).FirstOrDefault().Softwares) { listBox2.Items.Add(item.Name); softwares.Add(item); } foreach (var item in dataBase.Softwares) { bool check = true; foreach (var item1 in listBox2.Items) { if (item1.ToString() == item.Name) { check = false; break; } } if (check == true) { listBox1.Items.Add(item.Name); } } }