ASP.NET Tutorial/ADO.net Database/LINQ

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A grid with an empty data source.

<%@ Page Language="C#" %>
<!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>Empty Grid</title>
</head>
<body>
    <div id="pageContent">
        <form id="form1" runat="server">
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" EnableCaching="true"   
                ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"
                SelectCommand="SELECT customerid, companyname FROM customers WHERE customerid="none"">
        </asp:SqlDataSource> 
        <asp:gridview ID="Gridview1" runat="server" datasourceid="SqlDataSource1">
            <emptydatatemplate>
                <asp:label ID="Label1" runat="server">
                    There"s no data to show in this view.
                </asp:label>
            </emptydatatemplate>
        </asp:gridview>
        </form>
    </div>
</body>
</html>


Use Linq-to-DataSets to query against (typed) DataTables and DataSets using the LINQ syntax

<%@ Page Language="C#" 
         AutoEventWireup="true" 
         CodeFile="Default.aspx.cs" 
         Inherits="Default" %>
<!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 runat="server">
    <title>Linq-to-DataSets</title>
</head>
<body>
    <form id="form1" runat="server">
        <div id="pageContent">
            <asp:Button ID="Button1" runat="server" Text="First 10 Days of Jan98" onclick="Button1_Click" />
            <asp:GridView ID="GridView1" runat="server">
            </asp:GridView>    
        </div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Data.SqlClient;
using System.Collections;
using System.Linq;
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.Xml.Linq;
public partial class Default : System.Web.UI.Page
{
    protected void Button1_Click(object sender, EventArgs e)
    {
        string connString = "SERVER=(local);DATABASE=northwind;Trusted_Connection=yes;";
        string cmd = "SELECT * FROM customers;SELECT * FROM orders";
        SqlDataAdapter adapter = new SqlDataAdapter(cmd, connString);
        DataSet ds = new DataSet();
        adapter.Fill(ds);
        var customers = ds.Tables[0].AsEnumerable();
        var orders = ds.Tables[1].AsEnumerable();
        var data = from o in orders
                   join c in customers
                   on o.Field<string>("CustomerID") equals c.Field<string>("CustomerID")
                   where o.Field<DateTime>("OrderDate").Year == 1998 &&
                         o.Field<DateTime>("OrderDate").Month == 1 &&
                         o.Field<DateTime>("OrderDate").Day < 10
                   select new {OrderID=o.Field<int>("OrderID"), 
                                Company=c.Field<string>("CompanyName")};
        GridView1.DataSource = data; 
        GridView1.DataBind();
    }
}


use Linq-to-Objects to query against .NET collections using the LINQ syntax

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" 
    Inherits="Default" %>
<!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 runat="server">
    <title>Linq-to-Objects</title>
</head>
<body>
    <div id="pageContent">
        <form id="form2" runat="server">
            <asp:Button ID="Button1" runat="server" Text="Click" onclick="Button1_Click" />
        </form>
    </div>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Linq;
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.Xml.Linq;
public partial class Default : System.Web.UI.Page
{
    protected void Button1_Click(object sender, EventArgs e)
    {
        int[] fiboNumbers = new int[] { 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 };
        var data0 = from n in fiboNumbers
                   where n % 2 == 0
                   select n;
        Response.Write(data0.Count());
        Response.Write("<hr/>");
        var data1 = (from n in fiboNumbers
                    where n % 2 == 0 && n <10
                    select n).Sum();
        Response.Write(data1);
    }
}
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/ADO.net_Database/LINQ&oldid=2753»