ASP.NET Tutorial/ADO.net Database/IAsyncResult

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The Poll approach of working with asynchronous commands (C#)

<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Configuration" %>
<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection DBCon;
        SqlCommand Command = new SqlCommand();
        SqlDataReader OrdersReader;
        IAsyncResult ASyncResult;
        DBCon = new SqlConnection();
        DBCon.ConnectionString =
          ConfigurationManager.ConnectionStrings["DSN_NorthWind"].ConnectionString;
        Command.rumandText = 
                "SELECT TOP 5 Customers.rupanyName, Customers.ContactName, " +
                " Orders.OrderID, Orders.OrderDate, " +
                " Orders.RequiredDate, Orders.ShippedDate " +
                " FROM Orders, Customers " +
                " WHERE Orders.CustomerID = Customers.CustomerID " +
                " ORDER BY Customers.rupanyName, Customers.ContactName "
        Command.rumandType = CommandType.Text;
        Command.Connection = DBCon;
        DBCon.Open();
        ASyncResult = Command.BeginExecuteReader();
        while (!ASyncResult.IsCompleted)
        {
            System.Threading.Thread.Sleep(10);
        }
        OrdersReader = Command.EndExecuteReader(ASyncResult);
        gvOrders.DataSource = OrdersReader;
        gvOrders.DataBind();
        DBCon.Close();
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>The Poll Approach</title>
</head>
<body>
    <form id="form1" runat="server">
    <div><br />
    <asp:GridView ID="gvOrders" Runat="server" 
                    AutoGenerateColumns="False" Width="100%">
    <Columns>
        <asp:BoundField HeaderText="Company Name" 
            DataField="CompanyName"></asp:BoundField>
        <asp:BoundField HeaderText="Contact Name" 
            DataField="ContactName"></asp:BoundField>
        <asp:BoundField HeaderText="Order Date" 
            DataField="orderdate" DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Required Date" DataField="requireddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Shipped Date" DataField="shippeddate" 
            DataFormatString="{0:d}"></asp:BoundField>
    </Columns>
    </asp:GridView><br />
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
        <add name="DSN_Northwind" 
             connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"
             providerName="System.Data.SqlClient" />
    </connectionStrings>
</configuration>


The Poll approach of working with asynchronous commands (VB)

<%@ Page Language="VB" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Configuration" %>
<script runat="server">
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) 
        Dim DBCon As SqlConnection
        Dim Command As SqlCommand = New SqlCommand()
        Dim OrdersReader As SqlDataReader
        Dim ASyncResult As IAsyncResult
        DBCon = New SqlConnection()
        DBCon.ConnectionString = ConfigurationManager.ConnectionStrings("DSN_NorthWind").ConnectionString
        Command.rumandText = "SELECT TOP 5 Customers.rupanyName, Customers.ContactName, " & _
                " Orders.OrderID, Orders.OrderDate, " & _
                " Orders.RequiredDate, Orders.ShippedDate " & _
                " FROM Orders, Customers " & _
                " WHERE Orders.CustomerID = Customers.CustomerID " & _
                " ORDER BY Customers.rupanyName, Customers.ContactName "
        Command.rumandType = CommandType.Text
        Command.Connection = DBCon
        DBCon.Open()
        ASyncResult = Command.BeginExecuteReader()
        While Not ASyncResult.IsCompleted
            System.Threading.Thread.Sleep(10)
        End While
        OrdersReader = Command.EndExecuteReader(ASyncResult)
        gvOrders.DataSource = OrdersReader
        gvOrders.DataBind()
        DBCon.Close()
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>The Poll Approach</title>
</head>
<body>
    <form id="form1" runat="server">
    <div><br />
    <asp:GridView ID="gvOrders" Runat="server" 
                    AutoGenerateColumns="False" Width="100%">
    <Columns>
        <asp:BoundField HeaderText="Company Name" 
            DataField="CompanyName"></asp:BoundField>
        <asp:BoundField HeaderText="Contact Name" 
            DataField="ContactName"></asp:BoundField>
        <asp:BoundField HeaderText="Order Date" 
            DataField="orderdate" DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Required Date" DataField="requireddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Shipped Date" DataField="shippeddate" 
            DataFormatString="{0:d}"></asp:BoundField>
    </Columns>
    </asp:GridView><br />
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
        <add name="DSN_Northwind" 
             connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"
             providerName="System.Data.SqlClient" />
    </connectionStrings>
</configuration>


The wait approach of handling a single asynchronous process (C#)

<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Configuration" %>
<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection DBCon;
        SqlCommand Command = new SqlCommand();
        SqlDataReader OrdersReader;
        IAsyncResult ASyncResult;
        System.Threading.WaitHandle WHandle;
        DBCon = new SqlConnection();
        DBCon.ConnectionString = 
                ConfigurationManager.ConnectionStrings["DSN_NorthWind"].ConnectionString;
        Command.rumandText = "SELECT TOP 5 Customers.rupanyName, Customers.ContactName, " +
                " Orders.OrderID, Orders.OrderDate, " +
                " Orders.RequiredDate, Orders.ShippedDate " +
                " FROM Orders, Customers " +
                " WHERE Orders.CustomerID = Customers.CustomerID " +
                " ORDER BY Customers.rupanyName, Customers.ContactName ";
        Command.rumandType = CommandType.Text;
        Command.Connection = DBCon;
        DBCon.Open();
        ASyncResult = Command.BeginExecuteReader();
        WHandle = ASyncResult.AsyncWaitHandle;
        if (WHandle.WaitOne() == true)
        {
            OrdersReader = Command.EndExecuteReader(ASyncResult);
            gvOrders.DataSource = OrdersReader;
            gvOrders.DataBind();
            DBCon.Close();
        }
        else
        {
        }
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>The Wait Approach</title>
</head>
<body>
    <form id="form1" runat="server">
    <div><br />
    <asp:GridView ID="gvOrders" Runat="server" 
                    AutoGenerateColumns="False" Width="100%">
    <Columns>
        <asp:BoundField HeaderText="Company Name" 
            DataField="CompanyName"></asp:BoundField>
        <asp:BoundField HeaderText="Contact Name" 
            DataField="ContactName"></asp:BoundField>
        <asp:BoundField HeaderText="Order Date" 
            DataField="orderdate" DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Required Date" DataField="requireddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Shipped Date" DataField="shippeddate" 
            DataFormatString="{0:d}"></asp:BoundField>
    </Columns>
    </asp:GridView><br />
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
        <add name="DSN_Northwind" 
             connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"
             providerName="System.Data.SqlClient" />
    </connectionStrings>
</configuration>


The wait approach of handling a single asynchronous process (VB)

<%@ Page Language="VB" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Configuration" %>
<script runat="server">
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) 
        Dim DBCon As SqlConnection
        Dim Command As SqlCommand = New SqlCommand()
        Dim OrdersReader As SqlDataReader
        Dim ASyncResult As IAsyncResult
        Dim WHandle As Threading.WaitHandle
        DBCon = New SqlConnection()
        DBCon.ConnectionString = ConfigurationManager.ConnectionStrings("DSN_NorthWind").ConnectionString
        Command.rumandText = "SELECT TOP 5 Customers.rupanyName, Customers.ContactName, " & _
                " Orders.OrderID, Orders.OrderDate, " & _
                " Orders.RequiredDate, Orders.ShippedDate " & _
                " FROM Orders, Customers " & _
                " WHERE Orders.CustomerID = Customers.CustomerID " & _
                " ORDER BY Customers.rupanyName, Customers.ContactName ";
        Command.rumandType = CommandType.Text
        Command.Connection = DBCon
        DBCon.Open()
        ASyncResult = Command.BeginExecuteReader()
        WHandle = ASyncResult.AsyncWaitHandle
        If WHandle.WaitOne = True Then
            OrdersReader = Command.EndExecuteReader(ASyncResult)
            gvOrders.DataSource = OrdersReader
            gvOrders.DataBind()
            DBCon.Close()
        Else
        End If
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>The Wait Approach</title>
</head>
<body>
    <form id="form1" runat="server">
    <div><br />
    <asp:GridView ID="gvOrders" Runat="server" 
                    AutoGenerateColumns="False" Width="100%">
    <Columns>
        <asp:BoundField HeaderText="Company Name" 
            DataField="CompanyName"></asp:BoundField>
        <asp:BoundField HeaderText="Contact Name" 
            DataField="ContactName"></asp:BoundField>
        <asp:BoundField HeaderText="Order Date" 
            DataField="orderdate" DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Required Date" DataField="requireddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Shipped Date" DataField="shippeddate" 
            DataFormatString="{0:d}"></asp:BoundField>
    </Columns>
    </asp:GridView><br />
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
        <add name="DSN_Northwind" 
             connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"
             providerName="System.Data.SqlClient" />
    </connectionStrings>
</configuration>


Use of the WaitAny method of processing multiple asynchronous processes (C#)

<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Configuration" %>
<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection DBCon;
        SqlCommand OrdersCommand = new SqlCommand();
        SqlCommand CustCommand = new SqlCommand();
        SqlDataReader OrdersReader;
        SqlDataReader CustReader;
        IAsyncResult OrdersASyncResult;
        IAsyncResult CustAsyncResult;
        int WHIndex;
        System.Threading.WaitHandle[] WHandles = new System.Threading.WaitHandle[1];
        System.Threading.WaitHandle OrdersWHandle;
        System.Threading.WaitHandle CustWHandle;
        DBCon = new SqlConnection();
        DBCon.ConnectionString = ConfigurationManager.ConnectionStrings["DSN_NorthWind"].ConnectionString;
        CustCommand.rumandText = " SELECT * FROM Customers WHERE CompanyName = "A" ";
        CustCommand.rumandType = CommandType.Text;
        CustCommand.Connection = DBCon;
        OrdersCommand.rumandText = 
                " SELECT Customers.rupanyName, Customers.ContactName, " +
                " Orders.OrderID, Orders.OrderDate, " +
                " Orders.RequiredDate, Orders.ShippedDate " +
                " FROM Orders, Customers " +
                " WHERE Orders.CustomerID = Customers.CustomerID " +
                " AND Customers.rupanyName = "Alfreds Futterkiste" " +
                " ORDER BY Customers.rupanyName, Customers.ContactName ";
        OrdersCommand.rumandType = CommandType.Text;
        OrdersCommand.Connection = DBCon;
        DBCon.Open();
        CustAsyncResult = CustCommand.BeginExecuteReader();
        OrdersASyncResult = OrdersCommand.BeginExecuteReader();
        CustWHandle = CustAsyncResult.AsyncWaitHandle;
        OrdersWHandle = OrdersASyncResult.AsyncWaitHandle;
        WHandles[0] = CustWHandle;
        WHandles[1] = OrdersWHandle;
        for (int Index = 0; Index < 2; Index++ )
        {
            WHIndex = System.Threading.WaitHandle.WaitAny(WHandles);
            switch (WHIndex)
            {
                case 0:
                    CustReader = CustCommand.EndExecuteReader(CustAsyncResult);
                    gvCustomers.DataSource = CustReader;
                    gvCustomers.DataBind();
                    break;
                case 1:
                    OrdersReader = 
                       OrdersCommand.EndExecuteReader(OrdersASyncResult);
                    gvOrders.DataSource = OrdersReader;
                    gvOrders.DataBind();
                    break;
            }
        }
        DBCon.Close();
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>The Wait Any Approach</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:GridView ID="gvCustomers" Width="100%" Runat="server"></asp:GridView>
    <br /><br />
    <asp:GridView ID="gvOrders" Width="100%" AutoGenerateColumns="False"         
        Runat="server">
        <Columns>
        <asp:BoundField HeaderText="Company Name" 
            DataField="CompanyName"></asp:BoundField>
        <asp:BoundField HeaderText="Contact Name" 
            DataField="ContactName"></asp:BoundField>
        <asp:BoundField HeaderText="Order Date" DataField="orderdate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Required Date" DataField="requireddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Shipped Date" DataField="shippeddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        </Columns>
    </asp:GridView>
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
        <add name="DSN_Northwind" 
             connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"
             providerName="System.Data.SqlClient" />
    </connectionStrings>
</configuration>


Use of the WaitAny method of processing multiple asynchronous processes (VB)

<%@ Page Language="VB" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Configuration" %>
<script runat="server">
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) 
        Dim DBCon As SqlConnection
        Dim OrdersCommand As SqlCommand = New SqlCommand()
        Dim CustCommand As SqlCommand = New SqlCommand()
        Dim OrdersReader As SqlDataReader
        Dim CustReader As SqlDataReader
        Dim OrdersASyncResult As IAsyncResult
        Dim CustAsyncResult As IAsyncResult
        Dim WHIndex As Integer
        Dim WHandles(1) As Threading.WaitHandle
        Dim OrdersWHandle As Threading.WaitHandle
        Dim CustWHandle As Threading.WaitHandle
        DBCon = New SqlConnection()
        DBCon.ConnectionString = ConfigurationManager.ConnectionStrings("DSN_NorthWind").ConnectionString
        CustCommand.rumandText = " SELECT * FROM Customers WHERE CompanyName = "A" "
        CustCommand.rumandType = CommandType.Text
        CustCommand.Connection = DBCon
        OrdersCommand.rumandText = _
                " SELECT Customers.rupanyName, Customers.ContactName, " & _
                " Orders.OrderID, Orders.OrderDate, " & _
                " Orders.RequiredDate, Orders.ShippedDate " & _
                " FROM Orders, Customers " & _
                " WHERE Orders.CustomerID = Customers.CustomerID " & _
                " AND Customers.rupanyName = "Alfreds Futterkiste" " & _
                " ORDER BY Customers.rupanyName, Customers.ContactName "
        OrdersCommand.rumandType = CommandType.Text
        OrdersCommand.Connection = DBCon
        DBCon.Open ()
        CustAsyncResult = CustCommand.BeginExecuteReader()
        OrdersASyncResult = OrdersCommand.BeginExecuteReader()
        CustWHandle = CustAsyncResult.AsyncWaitHandle
        OrdersWHandle = OrdersASyncResult.AsyncWaitHandle
        WHandles(0) = CustWHandle
        WHandles(1) = OrdersWHandle
        For Index As Integer = 0 To 1
            WHIndex = Threading.WaitHandle.WaitAny(WHandles)
            Select Case WHIndex
                Case 0
                    CustReader = CustCommand.EndExecuteReader(CustAsyncResult)
                    gvCustomers.DataSource = CustReader
                    gvCustomers.DataBind()                    
                Case 1
                    OrdersReader = _
                       OrdersCommand.EndExecuteReader(OrdersASyncResult)
                    gvOrders.DataSource = OrdersReader
                    gvOrders.DataBind()
            End Select
        Next
        DBCon.Close()
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>The Wait Any Approach</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:GridView ID="gvCustomers" Width="100%" Runat="server"></asp:GridView>
    <br /><br />
    <asp:GridView ID="gvOrders" Width="100%" AutoGenerateColumns="False"         
        Runat="server">
        <Columns>
        <asp:BoundField HeaderText="Company Name" 
            DataField="CompanyName"></asp:BoundField>
        <asp:BoundField HeaderText="Contact Name" 
            DataField="ContactName"></asp:BoundField>
        <asp:BoundField HeaderText="Order Date" DataField="orderdate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Required Date" DataField="requireddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        <asp:BoundField HeaderText="Shipped Date" DataField="shippeddate" 
            DataFormatString="{0:d}"></asp:BoundField>
        </Columns>
    </asp:GridView>
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
        <add name="DSN_Northwind" 
             connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"
             providerName="System.Data.SqlClient" />
    </connectionStrings>
</configuration>
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/ADO.net_Database/IAsyncResult&oldid=2708»