C#Combobox控件

Sql數據庫Book中的表是BookInformation：主鍵是ID，自動增長;字段有BookName;

將字段BookName的值顯示在Combobox控件上，我們在窗體加載事件中，獲取Combobox控件下拉列表

 public partial class Form1 : Form
    {
        //定義數據源DataSet
        DataSet ds = new DataSet();
        //定義適配器對象SqlDataAdapter
        SqlDataAdapter adp = null;
        public Form1()
        {
            InitializeComponent();
        }

 

  //窗體加載事件，獲取Combobox控件下拉列表
        private void Form1_Load(object sender, EventArgs e)
        {
            string connStr = "Data Source=.\\SQLEXPRESS;Initial Catalog=Book;Integrated Security=True";
            SqlConnection conn = new SqlConnection(connStr);
            //DataSet和SqlDataAdapter組合不需要手動打開或關閉數據庫,SqlDataAdapter會操作。
            string sqlSelect = "select ID,BookName from BookInformation ";
            //實例化SqlDataAdapter對象
            adp = new SqlDataAdapter(sqlSelect, conn);
            //填充數據集
            if (this.ds.Tables["BookInformation"] != null)  //通過說明這個表中有數據
            {
                this.ds.Tables["BookInformation"].Clear();//清空表BookInformation裏的數據
            }
            adp.Fill(ds, "BookInformation");
            //給數據集中添加一行數據
            DataRow row = this.ds.Tables["BookInformation"].NewRow();
            row[0] = -1;
            row[1] = "請選擇";
            this.ds.Tables["BookInformation"].Rows.InsertAt(row, 0);
            //綁定數據
            this.cbBookName.DataSource = this.ds.Tables["BookInformation"];
            this.cbBookName.DisplayMember = "BookName";//界面顯示的值(要綁定的sql字段）
            this.cbBookName.ValueMember = "ID";//顯示項的實際值
        }

如何選中Combobox控件的值進行sql中的查找：

  string sqlSelect = "select * from BookInformation where ID='" +Convert.ToString(cbBookName.SelectedValue)+ "'";