ASP.NET Tutorial/ADO.net Database/SqlCommand

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Версия от 11:56, 26 мая 2010; Admin (обсуждение | вклад) (1 версия)
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Attach SqlCommand to DataGrid

<%@ Page Language="C#" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Data.SqlClient" %>
<script runat="server">
    void Page_Load(object sender, EventArgs e) {
        if (!Page.IsPostBack)
        {
            string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
            SqlConnection myConnection = new SqlConnection(ConnectionString);
    
            try{
                string CommandTextPublisher = "SELECT PublisherID, PublisherName FROM Publisher";
                SqlCommand myCommandPublishers = new SqlCommand(CommandTextPublisher, myConnection);
    
                myConnection.Open();
    
                DropDownList1.DataSource = myCommandPublishers.ExecuteReader();
                DropDownList1.DataTextField = "PublisherName";
                DropDownList1.DataValueField = "PublisherID";
                DropDownList1.DataBind();
                DropDownList1.Items.Insert(0, new ListItem("-- All Publishers --", "0"));
            }
            catch (Exception ex){
                throw(ex);
            }
            finally{
                myConnection.Close();
            }
        }
    }
    
    void ApplyFilter_Click(Object sender, EventArgs e) {
        string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
        SqlConnection myConnection = new SqlConnection(ConnectionString);
    
        try{
            string CommandTextBooks = "SELECT Book.BookTitle, Publisher.PublisherName FROM Book INNER JOIN Publisher on Book.BookPublisherID = Publisher.PublisherID";
            string filterValue = DropDownList1.SelectedValue;
            if (filterValue != "0")
                CommandTextBooks += " WHERE Book.BookPublisherID = " + filterValue;
            CommandTextBooks+=" ORDER BY Book.BookTitle";
            SqlCommand myCommandBooks = new SqlCommand(CommandTextBooks, myConnection);
    
            myConnection.Open();
    
            DataGrid1.DataSource = myCommandBooks.ExecuteReader();
            DataGrid1.DataBind();
        }
        catch (Exception ex){
            throw(ex);
        }
        finally{
            myConnection.Close();
        }
    }
</script>
<html>
<head>
</head>
<body>
    <form runat="server">
        
            Select a Publisher: 
            <asp:DropDownList id="DropDownList1" runat="server"></asp:DropDownList>
            &nbsp; 
            <asp:Button id="Button1" onclick="ApplyFilter_Click" runat="server" Text="Show Titles"></asp:Button>
        
        <asp:datagrid id="DataGrid1" runat="server" EnableViewState="False">
            <HeaderStyle font-bold="True" forecolor="white" backcolor="#4A3C8C"></HeaderStyle>
            <ItemStyle backcolor="#DEDFDE"></ItemStyle>
        </asp:datagrid>
    </form>
</body>
</html>

File: Web.config
<configuration>
    <appSettings>
        <add key="MSDEConnectString" value="server=(local)\YourDatabase;database=Books;uid=YourID;pwd=letmein;" />
    </appSettings>
</configuration>


Avoid SQL injection

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="SqlInjectionCorrected" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <asp:TextBox id="txtID" runat="server">ALFKI" OR "1"="1</asp:TextBox>
      <asp:Label id="Label1" runat="server">Enter Customer ID:</asp:Label>
      <asp:Button id="cmdGetRecords" runat="server" Text="Get Records" OnClick="cmdGetRecords_Click"></asp:Button>
      <asp:GridView id="GridView1" runat="server" Width="392px" Height="123px"></asp:GridView>
    </div>
    </form>
</body>
</html>

File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
public partial class SqlInjectionCorrected : System.Web.UI.Page
{
  protected void cmdGetRecords_Click(object sender, System.EventArgs e)
  {
    string connectionString = "Data Source=localhost;Initial Catalog=Northwind;" +
      "Integrated Security=SSPI";
    SqlConnection con = new SqlConnection(connectionString);
    string sql =
      "SELECT Orders.CustomerID, Orders.OrderID, COUNT(UnitPrice) AS Items, " +
      "SUM(UnitPrice * Quantity) AS Total FROM Orders " +
      "INNER JOIN [Order Details] " +
      "ON Orders.OrderID = [Order Details].OrderID " +
      "WHERE Orders.CustomerID = @CustID " +
      "GROUP BY Orders.OrderID, Orders.CustomerID";
    SqlCommand cmd = new SqlCommand(sql, con);
    cmd.Parameters.Add("@CustID", txtID.Text);
    con.Open();
    SqlDataReader reader = cmd.ExecuteReader();
    GridView1.DataSource = reader;
    GridView1.DataBind();
    reader.Close();
    con.Close();
  }
}


Avoid SQL Injection attack

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="AddShipper" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Add New Shipper</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h1>Add New Shipper</h1>
        <asp:Label ID="lblCompanyName" runat="server" Text="Company Name:"> </asp:Label> 
        <asp:TextBox ID="txtCompanyName" runat="server"></asp:TextBox>
        <br />
        <asp:Label ID="lblPhone" runat="server" Text="Phone:"> </asp:Label> <asp:TextBox ID="txtPhone"
            runat="server"></asp:TextBox><br />
        <br />
        <asp:Button ID="btnBadAddShipper" runat="server" Text="Bad Add Shipper" OnClick="btnBadAddShipper_Click" />
        <asp:Button ID="btnGoodAddShipper" runat="server" OnClick="btnGoodAddShipper_Click"
            Text="Good Add Shipper" /></div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class AddShipper : System.Web.UI.Page 
{
    protected void btnBadAddShipper_Click(object sender, EventArgs e)
    {
        string connStr = "Server=(local);Database=Northwind;Integrated Security=SSPI";
        string cmdStr =  "insert into Shippers (CompanyName, Phone) values ("" + 
            txtCompanyName.Text + "", "" + txtPhone.Text + "")";
        using (SqlConnection conn = new SqlConnection(connStr))
        using (SqlCommand cmd = new SqlCommand(cmdStr, conn))
        {
            conn.Open();
            cmd.ExecuteNonQuery();
        }
    }
    protected void btnGoodAddShipper_Click(object sender, EventArgs e)
    {
        string connStr = "Server=(local);Database=Northwind;Integrated Security=SSPI";
        
        string cmdStr = "insert into Shippers (CompanyName, Phone) values (" + "@CompanyName, @Phone)";
        using (SqlConnection conn = new SqlConnection(connStr))
        using (SqlCommand cmd = new SqlCommand(cmdStr, conn))
        {
            cmd.Parameters.AddWithValue("@CompanyName", txtCompanyName.Text);
            cmd.Parameters.AddWithValue("@Phone", txtPhone.Text);
            conn.Open();
            cmd.ExecuteNonQuery();
        }
    }
}


Browser Snoop

<% @ Page Language="VB" %>
<html>
<head>
   <title>Browser Snoop</title>
</head>
<body>
  <center><h1>Browser Capabilities</h1></center><hr/>
  <% 
        Response.Write("ActiveX Controls: " & Request.Browser.ActiveXControls & "<br/>")
        Response.Write("AOL: " & Request.Browser.AOL & "<br/>")
        Response.Write("Background Sounds: " & Request.Browser.BackgroundSounds & "<br/>")
        Response.Write("Beta: " & Request.Browser.Beta & "<br/>")
        Response.Write("CDF: " & Request.Browser.CDF & "<br/>")
        Response.Write("CLR Version: " & Request.Browser.ClrVersion.ToString() & "<br/>")
        Response.Write("Cookies: " & Request.Browser.Cookies & "<br/>")
        Response.Write("Crawler: " & Request.Browser.Crawler & "<br/>")
        Response.Write("ECMA Script Version: " & Request.Browser.EcmaScriptVersion.ToString() & "<br/>")
        Response.Write("Frames: " & Request.Browser.Frames & "<br/>")
        Response.Write("Java Applets: " & Request.Browser.JavaApplets & "<br/>")
        Response.Write("JavaScript: " & Request.Browser.JavaScript & "<br/>")
        Response.Write("Major Version: " & Request.Browser.MajorVersion & "<br/>")
        Response.Write("Minor Version: " & Request.Browser.MinorVersion & "<br/>")
        Response.Write("MS DOM Version: " & Request.Browser.MSDomVersion.ToString() & "<br/>")
        Response.Write("Platform: " & Request.Browser.Platform & "<br/>")
        Response.Write("Tables: " & Request.Browser.Tables & "<br/>")
        Response.Write("Tag Writer: " & Request.Browser.TagWriter.ToString() & "<br/>")
        Response.Write("Type: " & Request.Browser.Type & "<br/>")
        Response.Write("VBScript: " & Request.Browser.VBScript & "<br/>")
        Response.Write("W3C DOM Version: " & Request.Browser.W3CDomVersion.ToString() & "<br/>")
        Response.Write("Win16: " & Request.Browser.Win16 & "<br/>")
        Response.Write("Win32: " & Request.Browser.Win32 & "<br/>")
  %>
</body>
</html>


Create SqlCommand from sql statement and connection

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="DataReader" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <h2>Employees</h2>
    <asp:Literal runat="server" ID="HtmlContent" />
    </div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Text;
using System.Web.Configuration;
public partial class DataReader : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    string connectionString = WebConfigurationManager.ConnectionStrings["Northwind"].ConnectionString;
    SqlConnection con = new SqlConnection(connectionString);
    string sql = "SELECT * FROM Employees";
    SqlCommand cmd = new SqlCommand(sql, con);
    con.Open();
    SqlDataReader reader = cmd.ExecuteReader();
    StringBuilder htmlStr = new StringBuilder("");
    while (reader.Read())
    {
      htmlStr.Append("<li>");
      htmlStr.Append(reader["TitleOfCourtesy"]);
      htmlStr.Append(" <b>");
      htmlStr.Append(reader.GetString(1));
      htmlStr.Append("</b>, ");
      htmlStr.Append(reader.GetString(2));
      htmlStr.Append(" - employee from ");
      htmlStr.Append(reader.GetDateTime(6).ToString("d"));
      htmlStr.Append("</li>");
    }
    reader.Close();
    con.Close();
    HtmlContent.Text = htmlStr.ToString();
    }
}
File: Web.config
<?xml version="1.0"?>
<configuration xmlns="http://schemas.microsoft.ru/.NetConfiguration/v2.0">
  <connectionStrings>
    <add name="Northwind" connectionString="Data Source=localhost;Initial Catalog=Northwind;Integrated Security=SSPI"/>
  </connectionStrings>
  <appSettings>
    <add key="factory" value="System.Data.SqlClient" />
    <add key="employeeQuery" value="SELECT * FROM Employees" />
  </appSettings>
  <system.web>
    <compilation debug="true"/>
    <authentication mode="Windows"/>
  </system.web>
</configuration>


Execuate select command by using the SqlCommand

<%@ Page Language="C#" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Data.SqlClient" %>
<script runat="server">
    void Page_Load(object sender, EventArgs e) {
        string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
        string CommandText = "select PublisherID, PublisherName, PublisherCity, PublisherWebsite FROM Publisher ORDER BY PublisherID";
    
        SqlConnection myConnection = new SqlConnection(ConnectionString);
        SqlCommand myCommand = new SqlCommand(CommandText, myConnection);
    
        myConnection.Open();
    
        DataGrid1.DataSource = myCommand.ExecuteReader(CommandBehavior.CloseConnection);
        DataGrid1.DataBind();
    }
</script>
<html>
<head>
</head>
<body>
    <form runat="server">
        <asp:datagrid id="DataGrid1" runat="server" CellSpacing="1" GridLines="None" CellPadding="3" BackColor="White" ForeColor="Black" EnableViewState="False">
            <HeaderStyle font-bold="True" forecolor="white" backcolor="#4A3C8C"></HeaderStyle>
            <ItemStyle backcolor="#DEDFDE"></ItemStyle>
        </asp:datagrid>
    </form>
</body>
</html>
File: Web.config
<configuration>
    <appSettings>
        <add key="MSDEConnectString" value="server=(local)\YourDatabase;database=Books;uid=YourID;pwd=letmein;" />
    </appSettings>
</configuration>


Execute insert command by using SqlCommand

<%@ Page Language="C#" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Data.SqlClient" %>
<script runat="server">
   
    void Page_Load(object sender, EventArgs e) {
        string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
        SqlConnection myConnection = new SqlConnection(ConnectionString);
    
        try{
            string CommandText = "INSERT Publisher (PublisherName, PublisherCity, PublisherContact_Email, PublisherWebsite) VALUES ("New Publisher", "Newcastle", "bigcheese@newpublish.ru", "http://www.newpublish.ru")";
            SqlCommand myCommand = new SqlCommand(CommandText, myConnection);
    
            myConnection.Open();
    
            lblRecords.Text = Convert.ToString(myCommand.ExecuteNonQuery());
        }
        catch (Exception ex){
            throw(ex);
        }
        finally{
            myConnection.Close();
        }
    }
</script>
<html>
<head>
</head>
<body>
    <form runat="server">
        Records affected: <asp:Label id="lblRecords" runat="server"></asp:Label>
    </form>
</body>
</html>

File: Web.config
<configuration>
    <appSettings>
        <add key="MSDEConnectString" value="server=(local)\YourDatabase;database=Books;uid=YourID;pwd=letmein;" />
    </appSettings>
</configuration>


Execute update command

<%@ Page Language="C#" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Data.SqlClient" %>
<script runat="server">
    void Page_Load(object sender, EventArgs e) {
        string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
        SqlConnection myConnection = new SqlConnection(ConnectionString);
    
        try{
            string CommandText = "UPDATE Publisher Set PublisherName="Old Publisher", PublisherCity = "Manchester" WHERE PublisherID = 6";
            SqlCommand myCommand = new SqlCommand(CommandText, myConnection);
    
            myConnection.Open();
            lblRecords.Text = Convert.ToString(myCommand.ExecuteNonQuery());
        } catch (Exception ex){
            throw(ex);
        } finally{
            myConnection.Close();
        }
    }
</script>
<html>
<head>
</head>
<body>
    <form runat="server">
        Records affected: <asp:Label id="lblRecords" runat="server"></asp:Label>
    </form>
</body>
</html>
File: Web.config
<configuration>
    <appSettings>
        <add key="MSDEConnectString" value="server=(local)\YourDatabase;database=Books;uid=YourID;pwd=letmein;" />
    </appSettings>
</configuration>


Executing a Command

File: App_Code\Product.cs
using System;
using System.Data;
using System.Data.SqlClient;
using System.Web.Configuration;
using System.Collections.Generic;
public class Product
{
    private static readonly string _connectionString;
    private int _id;
    private string _title;
    private string _director;
    public int Id
    {
        get { return _id; }
        set { _id = value; }
    }
    public string Title
    {
        get { return _title; }
        set { _title = value; }
    }
    public string Director
    {
        get { return _director; }
        set { _director = value; }
    }
    public void Update(int id, string title, string director)
    {
        SqlConnection con = new SqlConnection(_connectionString);
        SqlCommand cmd = new SqlCommand("UPDATE ProductS SET Title=@Title,Director=@Director WHERE Id=@Id", con);
        cmd.Parameters.AddWithValue("@Title", title);
        cmd.Parameters.AddWithValue("@Director", director);
        cmd.Parameters.AddWithValue("@Id", id);
        using (con)
        {
            con.Open();
            cmd.ExecuteNonQuery();
        }
    }
    public void Delete(int id)
    {        
        SqlConnection con = new SqlConnection(_connectionString);
        SqlCommand cmd = new SqlCommand("DELETE ProductS WHERE Id=@Id", con);
        cmd.Parameters.AddWithValue("@Id", id);
        using (con)
        {
            con.Open();
            cmd.ExecuteNonQuery();
        }
    }
    public List<Product> GetAll()
    {
        List<Product> results = new List<Product>();
        SqlConnection con = new SqlConnection(_connectionString);
        SqlCommand cmd = new SqlCommand("SELECT Id,Title,Director FROM Products", con);
        using (con)
        {
            con.Open();
            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                Product newProduct = new Product();
                newProduct.Id = (int)reader["Id"];
                newProduct.Title = (string)reader["Title"];
                newProduct.Director = (string)reader["Director"];
                results.Add(newProduct);
            }
        }
        return results;
    }
    static Product()
    {
        _connectionString = WebConfigurationManager.ConnectionStrings["Products"].ConnectionString;
    }
}
File: Web.config
<configuration>
  <connectionStrings>
    <add name="Products" 
         connectionString="Data Source=.\SQLEXPRESS;
         AttachDbFilename=|DataDirectory|MyDatabase.mdf;Integrated Security=True;User Instance=True" />
  </connectionStrings>
</configuration>
    
File: index.aspx

<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Product</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:GridView
        id="grdProducts"
        DataSourceID="srcProducts"
        DataKeyNames="Id"
        AutoGenerateEditButton="true"
        AutoGenerateDeleteButton="true"
        Runat="server" />
    <asp:ObjectDataSource
        id="srcProducts"
        TypeName="Product"
        SelectMethod="GetAll"
        UpdateMethod="Update"
        DeleteMethod="Delete"
        Runat="server" />
    </div>
    </form>
</body>
</html>


Executing a Command with Parameters

File: App_Code\Product.cs
using System;
using System.Data;
using System.Data.SqlClient;
using System.Web.Configuration;
using System.Collections.Generic;
public class Product
{
    private static readonly string _connectionString;
    private int _id;
    private string _title;
    private string _director;
    public int Id
    {
        get { return _id; }
        set { _id = value; }
    }
    public string Title
    {
        get { return _title; }
        set { _title = value; }
    }
    public string Director
    {
        get { return _director; }
        set { _director = value; }
    }
    public void Update(int id, string title, string director)
    {
        SqlConnection con = new SqlConnection(_connectionString);
        SqlCommand cmd = new SqlCommand("ProductUpdate", con);
        cmd.rumandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@Id", id);        cmd.Parameters.AddWithValue("@Title", title);
        cmd.Parameters.AddWithValue("@Director", director);
        using (con)
        {
            con.Open();
            cmd.ExecuteNonQuery();
        }
    }
    public List<Product> GetAll()
    {
        List<Product> results = new List<Product>();
        SqlConnection con = new SqlConnection(_connectionString);
        SqlCommand cmd = new SqlCommand("ProductSelect", con);
        cmd.rumandType = CommandType.StoredProcedure;
        using (con)
        {
            con.Open();
            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                Product newProduct = new Product();
                newProduct.Id = (int)reader["Id"];
                newProduct.Title = (string)reader["Title"];
                newProduct.Director = (string)reader["Director"];
                results.Add(newProduct);
            }
        }
        return results;
    }
    static Product()
    {
        _connectionString = WebConfigurationManager.ConnectionStrings["Products"].ConnectionString;
    }
}
File: Web.config
<configuration>
  <connectionStrings>
    <add name="Products" 
         connectionString="Data Source=.\SQLEXPRESS;
         AttachDbFilename=|DataDirectory|MyDatabase.mdf;Integrated Security=True;User Instance=True" />
  </connectionStrings>
</configuration>
File: ProductStoredProcedures.sql
CREATE PROCEDURE dbo.ProductSelect
AS
SELECT Id, Title, Director FROM Products
CREATE PROCEDURE dbo.ProductUpdate
(
    @Id int,
    @Title NVarchar(100),
    @Director NVarchar(100)
)
AS
UPDATE Products SET
    Title = @Title,
    Director = @Director
WHERE Id = @Id

File: ShowProduct.aspx
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Product</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:GridView
        id="grdProducts"
        DataSourceID="srcProducts"
        DataKeyNames="Id"
        AutoGenerateEditButton="true"
        Runat="server" />
    <asp:ObjectDataSource
        id="srcProducts"
        TypeName="Product"
        SelectMethod="GetAll"
        UpdateMethod="Update"
        Runat="server" />
    </div>
    </form>
</body>
</html>


Executing Asynchronous Database Commands

File: App_Code\AsyncDataLayer.cs
using System;
using System.Data;
using System.Data.SqlClient;
using System.Web.Configuration;
using System.Collections.Generic;
public class AsyncDataLayer
{
    private static readonly string _connectionString;
    private SqlCommand _cmdProducts;
    public IAsyncResult BeginGetProducts(AsyncCallback callback, Object state)
    {
        SqlConnection con = new SqlConnection(_connectionString);
        _cmdProducts = new SqlCommand("WAITFOR DELAY "0:0:01";SELECT Title,Director FROM Products", con);
        con.Open();
        return _cmdProducts.BeginExecuteReader(callback, state, CommandBehavior.CloseConnection);
    }
    public List<AsyncDataLayer.Product> EndGetProducts(IAsyncResult result)
    {        
        List<AsyncDataLayer.Product> results = new List<AsyncDataLayer.Product>();
        SqlDataReader reader = _cmdProducts.EndExecuteReader(result);
        while (reader.Read())
        {
            AsyncDataLayer.Product newProduct = new AsyncDataLayer.Product();
            newProduct.Title = (string)reader["Title"];
            newProduct.Director = (string)reader["Director"];
            results.Add(newProduct);
        }
        return results;
    }
    static AsyncDataLayer()
    {
        _connectionString = WebConfigurationManager.ConnectionStrings["Products"].ConnectionString
            + ";Asynchronous Processing=true";
    }
    public class Product
    {
        private string _title;
        private string _director;
        public string Title
        {
            get { return _title; }
            set { _title = value; }
        }
        public string Director
        {
            get { return _director; }
            set { _director = value; }
        }
    }
}
File: Web.config
<configuration>
  <connectionStrings>
    <add name="Products" 
         connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|MyDatabase.mdf;Integrated Security=True;User Instance=True" />
  </connectionStrings>
</configuration>
File: Default.aspx
<%@ Page Language="C#" Async="true" AsyncTimeout="1" Trace="true" %>
<%@ Import Namespace="System.Threading" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    private AsyncDataLayer dataLayer = new AsyncDataLayer();
    void Page_Load()
    {
        PageAsyncTask task = new PageAsyncTask(BeginGetData, EndGetData, TimeoutData, null, true);
        Page.RegisterAsyncTask(task);
        Page.ExecuteRegisteredAsyncTasks();
    }
    IAsyncResult BeginGetData(object sender, EventArgs e, AsyncCallback callback, object state)
    {
        Trace.Warn("BeginGetData: " + Thread.CurrentThread.GetHashCode());
        return dataLayer.BeginGetProducts(callback, state);
    }
    void EndGetData(IAsyncResult ar)
    {
        Trace.Warn("EndGetDate: " + Thread.CurrentThread.GetHashCode());
        grdProducts.DataSource = dataLayer.EndGetProducts(ar);
        grdProducts.DataBind();
    }
    void TimeoutData(IAsyncResult ar)
    {
        lblError.Text = "Could not retrieve data!";
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Page AsyncTask</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:Label
        id="lblError"
        Runat="server" />
    <asp:GridView
        id="grdProducts"
        Runat="server" />
    </div>
    </form>
</body>
</html>


Pass a CommandBehavior.CloseConnection parameter to the ExecuteReader() method.

This parameter causes the database connection associated with the SqlDataReader to close automatically 
after all the records have been fetched from the SqlDataReader.
File: App_Code\Product.cs
using System;
using System.Data;
using System.Data.SqlClient;
using System.Web.Configuration;
using System.Collections.Generic;
public class Product
{
    private static readonly string _connectionString;
    public SqlDataReader GetAll()
    {
        SqlConnection con = new SqlConnection(_connectionString);
        SqlCommand cmd = new SqlCommand("SELECT Title,Director FROM Products", con);
        con.Open();
        return cmd.ExecuteReader(CommandBehavior.CloseConnection);
    }    
    static Product()
    {
        _connectionString = WebConfigurationManager.ConnectionStrings["Products"].ConnectionString;
    }
}
File: ShowProduct.aspx
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Product</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:GridView
        id="grdProducts"
        DataSourceID="srcProducts"
        Runat="server" />
    <asp:ObjectDataSource
        id="srcProducts"
        TypeName="Product"
        SelectMethod="GetAll"
        Runat="server" />
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
    <add name="Products" 
         connectionString="Data Source=.\SQLEXPRESS;
         AttachDbFilename=|DataDirectory|MyDatabase.mdf;Integrated Security=True;User Instance=True" />
  </connectionStrings>
</configuration>


Read scalar data by using SqlCommand

<%@ Page Language="C#" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Data.SqlClient" %>
<script runat="server">
    void Page_Load(object sender, EventArgs e) {
        string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
        string CommandText = "select PublisherID, PublisherName, PublisherCity, PublisherWebsite FROM Publisher ORDER BY PublisherID";
    
        SqlConnection myConnection = new SqlConnection(ConnectionString);
        SqlCommand myCommand = new SqlCommand(CommandText, myConnection);
    
        myConnection.Open();
    
        string CommandTextCount = "SELECT COUNT(*) FROM Publisher";
        SqlCommand myCommandCount = new SqlCommand(CommandTextCount, myConnection);
    
        lblTotal.Text = Convert.ToString(myCommandCount.ExecuteScalar());
    
        DataGrid1.DataSource = myCommand.ExecuteReader(CommandBehavior.CloseConnection);
        DataGrid1.DataBind();
    }
</script>
<html>
<head>
</head>
<body>
    <asp:Label id="lblTotal" runat="server"></asp:Label>
    <form runat="server">
        <asp:datagrid id="DataGrid1" runat="server" EnableViewState="False">
            <HeaderStyle font-bold="True" forecolor="white" backcolor="#4A3C8C"></HeaderStyle>
            <ItemStyle backcolor="#DEDFDE"></ItemStyle>
        </asp:datagrid>
    </form>
</body>
</html>
File: Web.config
<configuration>
    <appSettings>
        <add key="MSDEConnectString" value="server=(local)\YourDatabase;database=Books;uid=YourID;pwd=letmein;" />
    </appSettings>
</configuration>


Returning a Single Value

File: Default.aspx
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Web.Configuration" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    protected void btnSearch_Click(object sender, EventArgs e)
    {
        string connectionString = WebConfigurationManager.ConnectionStrings["Products"].ConnectionString;
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("SELECT Totals FROM Products WHERE Title=@Title", con);
        cmd.Parameters.AddWithValue("@Title", txtTitle.Text);
        using (con)
        {
            con.Open();
            Object result = cmd.ExecuteScalar();
            if (result != null)
                lblResult.Text = String.Format("{0:c}", result);
            else
                lblResult.Text = "No match!";
        }
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Execute Scalar</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <h1>Box Office Totals</h1>
    <asp:Label
        id="lblTitle"
        Text="Product Title:"
        AssociatedControlID="txtTitle"
        Runat="server" />
    <asp:TextBox
        id="txtTitle"
        Runat="server" />
    <asp:Button
        id="btnSearch"
        Text="Search"
        OnClick="btnSearch_Click"
        Runat="server" />
    <hr />
    <asp:Label
        id="lblResult"
        Runat="server" />
    </div>
    </form>
</body>
</html>
File: Web.config
<configuration>
  <connectionStrings>
    <add name="Products" 
         connectionString="Data Source=.\SQLEXPRESS;
         AttachDbFilename=|DataDirectory|MyDatabase.mdf;Integrated Security=True;User Instance=True" />
  </connectionStrings>
</configuration>
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/ADO.net_Database/SqlCommand&oldid=2702»