ADO.NET2.0增加了一些新的特性，其中就包括異步查詢。這個特點在需要執行多個查詢的時候，或者查詢過程比較常的時候就很有用。而默認情況下是不開啓異步查詢的，必須要在連接字符串中顯示的打開，如下圖，圖中劃線的就是需要顯示制定的，後面一個是顯示的打開MARS。
下面的代碼包括了異步查詢的三種方法，所以代碼都可以測試運行，數據庫是NorthWind.
其中一個運行頁面如圖：
首先是頁面源碼：
<form id="form1" runat="server"> <div> <asp:GridView ID="GridView1" runat="server" BackColor="White" BorderColor="#CCCCCC" BorderStyle="None" BorderWidth="1px" CellPadding="3"> <FooterStyle BackColor="White" ForeColor="#000066" /> <RowStyle ForeColor="#000066" /> <SelectedRowStyle BackColor="#669999" Font-Bold="True" ForeColor="White" /> <PagerStyle BackColor="White" ForeColor="#000066" HorizontalAlign="Left" /> <HeaderStyle BackColor="#006699" Font-Bold="True" ForeColor="White" /> </asp:GridView> </div> <asp:GridView ID="GridView2" runat="server" BackColor="White" BorderColor="#336666" BorderStyle="Double" BorderWidth="3px" CellPadding="4" GridLines="Horizontal"> <FooterStyle BackColor="White" ForeColor="#333333" /> <RowStyle BackColor="White" ForeColor="#333333" /> <SelectedRowStyle BackColor="#339966" Font-Bold="True" ForeColor="White" /> <PagerStyle BackColor="#336666" ForeColor="White" HorizontalAlign="Center" /> <HeaderStyle BackColor="#336666" Font-Bold="True" ForeColor="White" /> </asp:GridView> </form>
後臺代碼：
public string ConStr = ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString; protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindData(); //BindMultiData(); //BindMultiDataArray(); //BindDataWithCallBack();
} 
} //異步查詢的poll方式，最普通的方式 private void BindData() { string QueryStr = "SELECT * FROM customers"; using (SqlConnection Con = new SqlConnection(ConStr)) { SqlCommand Cmd = new SqlCommand(QueryStr, Con); IAsyncResult ASynResult; SqlDataReader Da; try { Con.Open(); //begin方法返回一個IAsyncResult對象，用來檢查執行是否完成 ASynResult = Cmd.BeginExecuteReader(CommandBehavior.CloseConnection); while (!ASynResult.IsCompleted) { Response.Write("異步查詢</br>"); ASynResult.AsyncWaitHandle.WaitOne(3000, true); //System.Threading.Thread.Sleep(10); } Da = Cmd.EndExecuteReader(ASynResult); GridView1.DataSource = Da; GridView1.DataBind(); } catch (Exception ex) { Response.Write(ex.Message); } } } //異步查詢的wait方式，使用多個等待句柄來異步查詢，必須等待所有進程完成處理結果集 private void BindMultiData() { string CusQueryStr = "SELECT * FROM customers WHERE CompanyName = 'Alfreds Futterkiste'"; string SupQueryStr = "SELECT Customers.CompanyName, Customers.ContactName, " + "Orders.OrderID, Orders.OrderDate, " + "Orders.RequiredDate, Orders.ShippedDate " + "FROM Orders, Customers " + "WHERE Orders.CustomerID = Customers.CustomerID " + "AND Customers.CompanyName = 'Alfreds Futterkiste' " + "ORDER BY Customers.CompanyName, Customers.ContactName"; using (SqlConnection MyCon = new SqlConnection(ConStr)) { SqlCommand CusCmd = new SqlCommand(CusQueryStr, MyCon); SqlCommand SupCmd = new SqlCommand(SupQueryStr, MyCon); SqlDataReader CusDr; SqlDataReader SupDr; IAsyncResult CusIsynResult; IAsyncResult SupIsynResult; //創建句柄數組 System.Threading.WaitHandle[] WHandles = new System.Threading.WaitHandle[2]; System.Threading.WaitHandle CusHandle; System.Threading.WaitHandle SupHandle; MyCon.Open(); CusIsynResult = CusCmd.BeginExecuteReader(CommandBehavior.CloseConnection); SupIsynResult = SupCmd.BeginExecuteReader(CommandBehavior.CloseConnection); CusHandle = CusIsynResult.AsyncWaitHandle; SupHandle = SupIsynResult.AsyncWaitHandle; //將等待句柄賦給句柄數組 WHandles[0] = CusHandle; WHandles[1] = SupHandle; //將數組傳給waitall方法，等待所以的異步查詢完成 System.Threading.WaitHandle.WaitAll(WHandles); CusDr = CusCmd.EndExecuteReader(CusIsynResult); SupDr = SupCmd.EndExecuteReader(SupIsynResult); GridView1.DataSource = CusDr; GridView1.DataBind(); GridView2.DataSource = SupDr; GridView2.DataBind(); MyCon.Dispose(); CusCmd.Dispose(); SupCmd.Dispose(); } } //採用WaitAny方式，優點是不用等待所有進程都完成才處理結果集 private void BindMultiDataArray() { string CusQueryStr = "SELECT * FROM customers WHERE CompanyName = 'Alfreds Futterkiste'"; string SupQueryStr = "SELECT Customers.CompanyName, Customers.ContactName, " + "Orders.OrderID, Orders.OrderDate, " + "Orders.RequiredDate, Orders.ShippedDate " + "FROM Orders, Customers " + "WHERE Orders.CustomerID = Customers.CustomerID " + "AND Customers.CompanyName = 'Alfreds Futterkiste' " + "ORDER BY Customers.CompanyName, Customers.ContactName"; using (SqlConnection MyCon = new SqlConnection(ConStr)) { SqlCommand CusCmd = new SqlCommand(CusQueryStr, MyCon); SqlCommand SupCmd = new SqlCommand(SupQueryStr, MyCon); SqlDataReader CusDr; SqlDataReader SupDr; IAsyncResult CusIsynResult; IAsyncResult SupIsynResult; System.Threading.WaitHandle[] WHandles = new System.Threading.WaitHandle[2]; System.Threading.WaitHandle CusHandle; System.Threading.WaitHandle SupHandle; int WHindex; MyCon.Open(); CusIsynResult = CusCmd.BeginExecuteReader(CommandBehavior.CloseConnection); SupIsynResult = SupCmd.BeginExecuteReader(CommandBehavior.CloseConnection); CusHandle = CusIsynResult.AsyncWaitHandle; SupHandle = SupIsynResult.AsyncWaitHandle; WHandles[0] = CusHandle; WHandles[1] = SupHandle; for (int i = 0; i < WHandles.Length; i++) { //waitany好處在於不必等待所有異步操作完成 WHindex = System.Threading.WaitHandle.WaitAny(WHandles); switch (WHindex) { case 0: CusDr = CusCmd.EndExecuteReader(CusIsynResult); GridView1.DataSource = CusDr; GridView1.DataBind(); break; case 1: SupDr = SupCmd.EndExecuteReader(SupIsynResult); GridView2.DataSource = SupDr; GridView2.DataBind(); break; } } MyCon.Dispose(); CusCmd.Dispose(); SupCmd.Dispose(); } } //通過回調來實現異步查詢 private void BindDataWithCallBack() { string SupQueryStr = "SELECT Customers.CompanyName, Customers.ContactName, " + "Orders.OrderID, Orders.OrderDate, " + "Orders.RequiredDate, Orders.ShippedDate " + "FROM Orders, Customers " + "WHERE Orders.CustomerID = Customers.CustomerID " + "AND Customers.CompanyName = 'Alfreds Futterkiste' " + "ORDER BY Customers.CompanyName, Customers.ContactName"; using (SqlConnection MyCon = new SqlConnection(ConStr)) { SqlCommand SupCmd = new SqlCommand(SupQueryStr, MyCon); SqlDataReader SupDr; IAsyncResult SupIsynResult; MyCon.Open(); AsyncCallback Callback = new AsyncCallback(CallBackMethod); SupIsynResult = SupCmd.BeginExecuteReader(Callback, SupCmd,CommandBehavior.CloseConnection); System.Threading.Thread.Sleep(100); MyCon.Dispose(); SupCmd.Dispose(); } } //回調方法 public void CallBackMethod(IAsyncResult IResult) { SqlCommand Command = (SqlCommand)IResult.AsyncState; SqlDataReader dr = Command.EndExecuteReader(IResult); GridView1.DataSource = dr; GridView1.DataBind(); }}