ASP.NET Tutorial/ADO.net Database/LINQ
A grid with an empty data source.
<source lang="csharp">
<%@ 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>
<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>
</body> </html></source>
Use Linq-to-DataSets to query against (typed) DataTables and DataSets using the LINQ syntax
<source lang="csharp">
<%@ 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">
<asp:Button ID="Button1" runat="server" Text="First 10 Days of Jan98" onclick="Button1_Click" />
<asp:GridView ID="GridView1" runat="server">
</asp:GridView>
</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();
}
}</source>
use Linq-to-Objects to query against .NET collections using the LINQ syntax
<source lang="csharp">
<%@ 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>
<form id="form2" runat="server">
<asp:Button ID="Button1" runat="server" Text="Click" onclick="Button1_Click" />
</form>
</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("");
var data1 = (from n in fiboNumbers
where n % 2 == 0 && n <10
select n).Sum();
Response.Write(data1);
}
}</source>
