//動態綁定下拉框
string sql = "select id ,name form B ";
DataTable dt = DBHelper.GetDataTable(sql);
//綁定數據源
this.comboBox1.DataSource = dt;
//綁定要顯示的文本的字段
this.comboBox1.DisplayMember = "name";
//綁定真實的值value
this.comboBox1.valueMember = "id";

//彈出下拉框的值或文本

string name = this.comboBox1.Text;
string id = this.comboBox1.SelectdValue.ToString();
MessageBox.Show(name);

動態綁定下拉框