public CourseCatalogControl() { InitializeComponent(); SetCol(); IsRefresh = true; CourseSqlMapDao dal = new CourseSqlMapDao(); IList <Course> list = dal.CourseFindAll(); txt_CourseID.Properties.ValueMember = "CourseID"; txt_CourseID.Properties.DisplayMember = "CourseName"; txt_CourseID.Properties.DataSource = list.ToList(); txt_CourseID.EditValue = list[0].CourseID; }