private void comboBox3_SelectedIndexChanged(object sender, EventArgs e) { if (comboBox3.SelectedIndex < 0) { MessageBox.Show("Select Category!!!!"); } else { string catName = comboBox3.SelectedItem.ToString(); CategorySer catS = new CategorySer(); int catID = catS.GetCategoryID(catName, LogIn.user_ID); ShareTaskSer tS = new ShareTaskSer(); List <int> tkIDList = tS.GetAllTasksFromShareTasks(catID); TaskSer taskService; string tittle; for (int i = 0; i < tkIDList.Count; i++) { taskService = new TaskSer(); tittle = taskService.GetTaskTittle(catID, tkIDList[i]); cBCategory.Items.Add(tittle); } } }