This tutorial was created with Microsoft Visual Studio .NET 2008. However, if you are using 2005, you can implement LINQ by downloading Microsoft's LINQ Community Technology Preview release from here.
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In this tutorial, we will be looking at using LINQ to SQL Classes in conjunction with the ObjectDataSource control. We will be using a SQL database, and then representing that with a LINQ to SQL class. We will then build our own class that will use the LINQ to SQL class to interact with our database. We can then reference the method we build by our ObjectDataSource.
It may seem like a long process, but Visual Studio.NET does most of the work for us.
We will start out by creating a database - or if you have your own, you can use that. For this example, we will be using a SQL database with one table, and three columns - id, name, city.
Once we have our database set up and have added some sample data to it, we can create our LINQ to SQL class. Right-click our project in Solution Explorer and choose Add New Item, LINQ to SQL Classes. In this example, we named it People.dbml
This creates a class to represent our database.
Once this has been created, we can drag onto the designer area our table from Server Explorer, then Save.
Now we want to add our own class (Right-click project, Add New Item, Class). We want it in the App_Code folder. In this class, we will write a method to select the data from the database, order it, and then return. Our method will look something like this:
public static IEnumerable<tblPeople> Select()
{
PeopleDataContext dBase = new PeopleDataContext();
return dBase.tblPeoples.OrderBy(p=>p.name);
} |
Here, we use LINQ to first instantiate our LINQ to SQL class, and then return an ordered collection of data.
The entire class looks like this:
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Data.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Collections.Generic;
/// <summary>
/// Summary description for People
/// </summary>
public class People
{
public static IEnumerable<tblPeople> Select()
{
PeopleDataContext dBase = new PeopleDataContext();
return dBase.tblPeoples.OrderBy(p=>p.name);
}
public People()
{
//
// TODO: Add constructor logic here
//
} |
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A snippet from our LINQ to SQL class (which is generated by VS), which represents our database table follows:
public tblPeople()
{
OnCreated();
}
[Column(Storage="_id", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
public int id
{
get
{
return this._id;
}
set
{
if ((this._id != value))
{
this.OnidChanging(value);
this.SendPropertyChanging();
this._id = value;
this.SendPropertyChanged("id");
this.OnidChanged();
}
}
[Column(Storage="_name", DbType="VarChar(50)")]
public string name
{
get
{
return this._name;
}
set
{
if ((this._name != value))
{
this.OnnameChanging(value);
this.SendPropertyChanging();
this._name = value;
this.SendPropertyChanged("name");
this.OnnameChanged();
}
}
[Column(Storage="_city", DbType="VarChar(50)")]
public string city
{
get
{
return this._city;
}
set
{
if ((this._city != value))
{
this.OncityChanging(value);
this.SendPropertyChanging();
this._city = value;
this.SendPropertyChanged("city");
this.OncityChanged();
}
} |
We can then simply implement this into our web application using a GridView and an ObjectDataSource control. The DataSource will use the Select Method we just created, when we specify its SelectMethod. The TypeName refers to the class we created. The ASPX page will look something like this:
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<form id="form1" runat="server">
Alphabetically Ordered By Name using LINQ and ObjectDataSource:<br />
<asp:GridView ID="GridView1" runat="server" DataSourceID="ObjectDataSource1"
Width="408px" />
<asp:ObjectDataSource ID="ObjectDataSource1" runat="server" TypeName="People" SelectMethod="Select" /> |
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