ASP.NET 2.0 Everyday Apps For Dumies 2006 phần 9 potx

EventArgs e)

{

string con = WebConfigurationManager ➝5

.ConnectionStrings[“ForumConnectionString”]

.ConnectionString;

ds = new DataSet(); ➝6

// fill the Forums table ➝7

string sel = “SELECT [forumid], [name] “

+ “FROM Forums “

+ “ORDER BY [name]”;

SqlDataAdapter da = new SqlDataAdapter(sel, con);

da.Fill(ds, “Forums”);

// fill the Topics table ➝8

sel = “SELECT [forumid], [topicid], “

+ “[name], [description] “

+ “FROM Topics “

+ “ORDER BY [name]”;

da = new SqlDataAdapter(sel, con);

da.Fill(ds, “Topics”);

// bind the Forum repeater ➝9

ForumRepeater.DataSource = ds.Tables[“Forums”]

.DefaultView;

ForumRepeater.DataBind();

}

public void ForumRepeater_ItemDataBound( ➝10

Object sender, RepeaterItemEventArgs e)

{

Repeater r = ((Repeater)e.Item ➝11

.FindControl(“TopicRepeater”));

DataRowView drv ➝12

= (DataRowView)e.Item.DataItem;

string forumid = drv[“forumid”].ToString();

DataView dv ➝13

= ds.Tables[“Topics”].DefaultView;

dv.RowFilter = “forumid=” + forumid;

r.DataSource = dv; ➝14

r.DataBind();

}

}

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Here’s a set of 14 explanations, matched to the 14 key lines of this listing:

➝ 1 The code-behind file needs access to the System.Web.

Configuration namespace because it uses the

WebConfigurationManager class to retrieve the database

connection string from the web.config file.

➝ 2 The System.Data.SqlClient namespace is required to use

ADO.NET classes such as DataSet, SqlConnection, and

SqlCommand.

➝ 3 This line defines a class instance variable of type DataSet. That

way, the dataset will be available to both of the methods in the

code-behind file.

➝ 4 The Page_Load method executes when the page loads. It fills the

dataset with data retrieved from the Forums and Topics tables; it

also sets up data binding for the ForumRepeater control and calls

that control’s DataBind method, which completes the binding.

➝ 5 This line retrieves the connection string from the web.config

file.

➝ 6 This statement creates an empty dataset object and assigns it to

the ds variable.

➝ 7 These lines create a table in the ds dataset named Forums by a)

creating a data adapter that retrieves rows from the Forums table

and b) calling the data adapter’s Fill method.

➝ 8 These lines create a second table in the dataset (named Topics)

by creating a data adapter (which retrieves data from this new

Topics table) and calling the data adapter’s Fill method.

➝ 9 These lines set the data source for the ForumRepeater control

to the Forums table in the dataset, and then call the DataBind

method to bind the Repeater control to its data.

➝ 10 This method is called each time an item is bound to the outer

Repeater. It binds the inner Repeater control to the topics

that are associated with the forum represented by the item.

➝ 11 The e argument includes a property named Item that represents the

item being bound. This statement calls that item’s FindControl

method to find the Repeater control named TopicRepeater.

That particular Repeater is then assigned to the variable named

r so it can be used later.

➝ 12 These lines retrieve the id of the forum represented by the cur￾rent Repeater item. First, e.Item.DataItem is used to retrieve

a DataRowView object that lets you access the individual data

fields for the Repeater item. Then the forumid field is retrieved

and saved in a local variable named forumid.

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➝ 13 These lines retrieve a DataView object for the Topics table of

the data set and set its row filter so it views only those rows

whose forumid field matches the value of the forumid variable.

➝ 14 These lines bind the Repeater control to the data view. This

causes the Repeater control to create a line for each topic that’s

associated with the forum.

Listing 10-5: The code-behind file for the home page (VB version)

Imports System.Web.Configuration ➝1

Imports System.Data.SqlClient ➝2

Imports System.Data

Partial Class _Default

Inherits System.Web.UI.Page

Private ds As DataSet ➝3

Protected Sub Page_Load( _ ➝4

ByVal sender As Object, _

ByVal e As System.EventArgs) _

Handles Me.Load

Dim con As String _ ➝5

= WebConfigurationManager _

.ConnectionStrings(“ForumConnectionString”) _

.ConnectionString

ds = New DataSet() ➝6

‘fill the Forums table ➝7

Dim sel As String _

= “SELECT [forumid], [name] “ _

+ “FROM Forums “ _

+ “ORDER BY [name]”

Dim da As SqlDataAdapter _

= New SqlDataAdapter(sel, con)

da.Fill(ds, “Forums”)

‘fill the Topics table ➝8

sel = “SELECT [forumid], [topicid], “ _

+ “[name], [description] “ _

+ “FROM Topics “ _

+ “ORDER BY [name]”

da = New SqlDataAdapter(sel, con)

da.Fill(ds, “Topics”)

‘bind the Forum repeater ➝9

ForumRepeater.DataSource = ds.Tables(“Forums”) _

.DefaultView

ForumRepeater.DataBind()

End Sub

(continued)

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Listing 10-5 (continued)

Protected Sub ForumRepeater_ItemDataBound( _ ➝10

ByVal sender As Object, _

ByVal e As RepeaterItemEventArgs) _

Handles ForumRepeater.ItemDataBound

Dim r As Repeater ➝11

r = e.Item.FindControl(“TopicRepeater”)

Dim drv As DataRowView ➝12

drv = e.Item.DataItem

Dim forumid As String = drv(“forumid”)

Dim dv As DataView ➝13

dv = ds.Tables(“Topics”).DefaultView

dv.RowFilter = “forumid=” + forumid

r.DataSource = dv ➝14

r.DataBind()

End Sub

End Class

Building the Threads Page

The Threads page displays all threads for the topic selected by the user. The

Threads page knows which topic to display because the topic is passed as a

query string field from the Default.aspx page. Then the Threads page uses

a simple GridView control bound to a SqlDataSource to retrieve and dis￾play the threads.

A code-behind file is required to handle the Click event raised by the Start

a New Thread link or the SelectedItemChanged event raised by the

GridView control.

The Threads.aspx page

Listing 10-6 presents the .aspx code for the Threads page. There’s nothing

unusual about the code for this page, so you shouldn’t have much trouble

following it.

Listing 10-6: The Threads.aspx page

<%@ Page Language=”C#” ➝1

MasterPageFile=”~/MasterPage.master”

AutoEventWireup=”true”

CodeFile=”Threads.aspx.cs”

Inherits=”Threads”

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Title=”Topic Threads” %>

<asp:Content ID=”Content1” Runat=”Server” ➝2

ContentPlaceHolderID=”ContentPlaceHolder1” >

<asp:FormView ID=”FormView1” runat=”server” ➝3

DataSourceID=”SqlDataSource1”>

<ItemTemplate>

<h2>

<asp:Label ID=”nameLabel” runat=”server”

Text=’<%# Bind(“name”) %>’ />

</h2>

<h3>

<asp:Label ID=”descriptionLabel”

runat=”server”

Text=’<%# Bind(“description”) %>’ />

</h3>

</ItemTemplate>

</asp:FormView>

<asp:SqlDataSource ID=”SqlDataSource1” ➝4

runat=”server”

ConnectionString=”<%$ ConnectionStrings

:ForumConnectionString %>”

SelectCommand=”SELECT [name], [description]

FROM [Topics] WHERE ([topicid] = @topicid)”>

<SelectParameters>

<asp:QueryStringParameter ➝5

Name=”topicid”

QueryStringField=”topic”

Type=”Int32” />

</SelectParameters>

</asp:SqlDataSource>

<br />

<asp:GridView ID=”GridView1” runat=”server” ➝6

AutoGenerateColumns=”False”

DataSourceID=”SqlDataSource2”

DataKeyNames=”threadid”

AllowPaging=”True”

PageSize=”15”

PagerSettings-Mode=”NumericFirstLast”

OnSelectedIndexChanged

=”GridView1_SelectedIndexChanged”>

<Columns>

<asp:ButtonField ➝7

CommandName=”Select”

DataTextField=”subject”

HeaderText=”Subject”

Text=”Button”>

<ItemStyle HorizontalAlign=”Left”

Width=”250px” />

<HeaderStyle HorizontalAlign=”Left” />

</asp:ButtonField>

<asp:BoundField ➝8

DataField=”author”

HeaderText=”Author” >

(continued)

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Listing 10-6 (continued)

<HeaderStyle HorizontalAlign=”Left” />

<ItemStyle Width=”100px” />

</asp:BoundField>

<asp:BoundField ➝9

DataField=”replies”

HeaderText=”Replies” >

<HeaderStyle HorizontalAlign=”Center” />

<ItemStyle HorizontalAlign=”Center”

Width=”70px” />

</asp:BoundField>

<asp:BoundField ➝10

DataField=”lastpostdate”

HeaderText=”Last Post”

DataFormatString=”{0:d}” >

<HeaderStyle HorizontalAlign=”Center” />

<ItemStyle Width=”70px” />

</asp:BoundField>

</Columns>

</asp:GridView>

<asp:SqlDataSource ID=”SqlDataSource2” ➝11

runat=”server”

ConnectionString=”<%$ ConnectionStrings

:ForumConnectionString %>”

SelectCommand=”SELECT [threadid], [topicid],

[subject], [replies], [author], [lastpostdate]

FROM [Threads]

WHERE ([topicid] = @topicid)

ORDER BY [lastpostdate]”>

<SelectParameters>

<asp:QueryStringParameter ➝12

Name=”topicid”

QueryStringField=”topic”

Type=”Int32” />

</SelectParameters>

</asp:SqlDataSource>

<br />

<asp:LinkButton ID=”LinkButton1” ➝13

runat=”server”

Text=”Start a New Thread”

OnClick=”LinkButton1_Click” />

<br /><br />

<asp:LinkButton ID=”btnReturn” ➝14

runat=”server”

PostBackUrl=”~/Default.aspx”

Text=”Return to Forum Page” />

</asp:Content>

This listing has 14 key points to explain:

➝ 1 If you use the Visual Basic version of the code-behind file, be sure

to change the Language, AutoEventWireup, and CodeFile

attributes in the Page directive.

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