how would I add a ComboBox to the code below

dbCmd = new SqlCommand("INSERT INTO Problem(ProbDateTime,ReportingUser,MachineID,CurrenyDirectory,ProbComment,MachineLDrives)VALUES(@ProbDT,@Reporting,@MacID,@Directory,@Comment,@MachineLDrives)", sConn);
dbCmd.Parameters.AddWithValue("@ProbDT", dateTimePicker1.Text);
dbCmd.Parameters.AddWithValue("@Reporting", txtUser.Text);
dbCmd.Parameters.AddWithValue("@MacID", txtMachine.Text = Environment.MachineName);
dbCmd.Parameters.AddWithValue("@Directory", txtCurrDirectory.Text = Environment.CurrentDirectory);
dbCmd.Parameters.AddWithValue("@Comment", txtProbCom.Text);
dbCmd.Parameters.AddWithValue("@MachineLDrives", txtMachineDrives.Text);