This tutorial will show you how to use LINQ in conjunction with the ObjectDataSource to enable you to sort the data in a descending format. VB version.
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In this tutorial, we will be looking at how we can use 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.
Although it may seem like a long process, Visual Studio.NET actually 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. Make sure you save it after draggin on the table we will be using.
Now, to add our own class, Right-click the project in Solution Explorer, 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 Shared Function [Select]() As IEnumerable(Of tblPeople)
Dim dBase As New PeopleDataContext()
Return dBase.tblPeoples.OrderBy(Function(p) p.name) End Function |
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:
Imports Microsoft.VisualBasic
Public Class People
Public Shared Function [Select]() As IEnumerable(Of tblPeople)
Dim dBase As New PeopleDataContext()
Return dBase.tblPeoples.OrderBy(Function(p) p.name) End Function |
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A snippet from our LINQ to SQL class (which is generated by VS), which represents our database table follows:
| Public Sub New()
MyBase.New
OnCreated End Sub
<Column(Storage:="_id", AutoSync:=AutoSync.OnInsert, DbType:="Int NOT NULL IDENTITY", IsPrimaryKey:=true, IsDbGenerated:=true)> _
Public Property id() As Integer
Get
Return Me._id End Get Set
If ((Me._id = value) _
= false) Then
Me.OnidChanging(value)
Me.SendPropertyChanging
Me._id = value
Me.SendPropertyChanged("id")
Me.OnidChanged End If End Set
<Column(Storage:="_name", DbType:="VarChar(50)")> _
Public Property name() As String
Get
Return Me._name End Get Set
If (String.Equals(Me._name, value) = false) Then
Me.OnnameChanging(value)
Me.SendPropertyChanging
Me._name = value
Me.SendPropertyChanged("name")
Me.OnnameChanged End If End Set
<Column(Storage:="_city", DbType:="VarChar(50)")> _
Public Property city() As String
Get
Return Me._city End Get Set
If (String.Equals(Me._city, value) = false) Then
Me.OncityChanging(value)
Me.SendPropertyChanging
Me._city = value
Me.SendPropertyChanged("city")
Me.OncityChanged End If End Set |
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:
<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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