动态加载用户控件至DataList并为用户控件赋值实例演示

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为了实现这个演示，Insus.NET使用通用的新闻例子，它类别(目录)以及文章。在一个页面，显示所有类别，每个目录下显示最新几条新闻。

效果如下：
目录是用DataList控件显示，而文章标题列表是一个用户控件显示，这个用户控件将动态被加入至DataList。

复制代码代码如下:

 
View Code 
<asp:Repeater ID="Repeater1" runat="server" OnItemDataBound="Repeater1_ItemDataBound"> 
<HeaderTemplate> 
<table cellpadding="5" cellspacing="0" width="100%"> 
</HeaderTemplate> 
<ItemTemplate> 
<tr style="height: 30px; line-height: 10px;"> 
<td> 
$ 
</td> 
<td> 
<asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl='<%# "~/ArticleView.aspx?ID=" & Eval("Article_nbr")%>' ToolTip='<%# Eval("Subject")%>' Target="_blank"></asp:HyperLink> 
</td> 
<td> 
<%# objInsusDateTimeUtility.GetDateTime(Eval("PublicDate"), "yyyy-MM-dd")%> 
</td> 
</tr> 
</ItemTemplate> 
<FooterTemplate> 
</table> 
</FooterTemplate> 
</asp:Repeater> 

复制代码代码如下:

 
View Code 
View Code 
Imports System.Data 
Imports Insus.NET 
Partial Class AscxControls_ArticleList 
Inherits System.Web.UI.UserControl 
Implements ISetValue '继承接口 
Dim objArticle As New Article() 
Protected objInsusDateTimeUtility As New InsusDateTimeUtility() 
Private _DataSource As Object 
Private _SubjectLength As Integer = 20 
Public WriteOnly Property SubjectLength() As Integer 
Set(ByVal value As Integer) 
_SubjectLength = value 
End Set 
End Property 
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load 
Data_Binding() 
End Sub 
'绑定数据至Repeater控件 
Private Sub Data_Binding() 
Me.Repeater1.DataSource = _DataSource 
Me.Repeater1.DataBind() 
End Sub 
Protected Sub Repeater1_ItemDataBound(ByVal sender As Object, ByVal e As RepeaterItemEventArgs) 
Dim objDrv As DataRowView = DirectCast(e.Item.DataItem, DataRowView) 
If e.Item.ItemType = ListItemType.AlternatingItem OrElse e.Item.ItemType = ListItemType.Item Then 
If e.Item.FindControl("HyperLink1") IsNot Nothing Then 
Dim LinkSubject As HyperLink = DirectCast(e.Item.FindControl("HyperLink1"), HyperLink) 
If objDrv("Subject").Length > _SubjectLength Then 
LinkSubject.Text = objDrv("Subject").Substring(0, _SubjectLength) & "..." 
Else 
LinkSubject.Text = objDrv("Subject").ToString() 
End If 
End If 
End If 
End Sub 
'实现接口 
Public Sub SetValue(str As Object) Implements ISetValue.SetValue 
Me._DataSource = str 
End Sub 
End Class 

上面用户控件中，有一个接口：

复制代码代码如下:

 
ISetValue 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
namespace Insus.NET 
{ 
public interface ISetValue 
{ 
void SetValue(object obj); 
} 
} 

显示目录：

复制代码代码如下:

 
View Code 
<asp:DataList ID="DataListCatalog" runat="server" RepeatColumns="2" RepeatDirection="Horizontal" DataKeyField="Catalog_nbr" OnItemDataBound="DataListCatalog_ItemDataBound"> 
<ItemTemplate> 
<div style="padding:2PX; height:25px; background-color:#cbfb25; font-weight:bold; line-height:25PX;"> 
<%# Eval("CatalogName")%> 
</div> 
<asp:PlaceHolder ID="PlaceHolderArticleList" runat="server"></asp:PlaceHolder> 
</ItemTemplate> 
</asp:DataList> 

从数据库获取数据并绑定至目录的DataList控件。

复制代码代码如下:

 
View Code 
Imports Insus.NET 
Partial Class Index 
Inherits System.Web.UI.Page 
Dim objCatalog As New Catalog() 
Dim objArticle As New Article() 
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load 
If Not IsPostBack Then 
Data_Binding() 
End If 
End Sub 
Private Sub Data_Binding() 
objCatalog.IsActive = True 
Me.DataListCatalog.DataSource = objCatalog.GetByIsActive() 
Me.DataListCatalog.DataBind() 
End Sub 
End Class 

下面是重点，就是OnItemDataBound事件，在这个事件中，需要找到asp:PlaceHolder控件，这个容器将用来加载用户控件。

复制代码代码如下:

 
Protected Sub DataListCatalog_ItemDataBound(sender As Object, e As DataListItemEventArgs) 
If e.Item.ItemType = ListItemType.Item OrElse e.Item.ItemType = ListItemType.AlternatingItem Then 
'判断asp:PlaceHolder是否存在 
If e.Item.FindControl("PlaceHolderArticleList") IsNot Nothing Then 
Dim ctllaceHolder As PlaceHolder = DirectCast(e.Item.FindControl("PlaceHolderArticleList"), PlaceHolder) 
'动态加载用户控件，并转换为接口。 
Dim objuc As ISetValue = DirectCast(LoadControl("~/AscxControls/ArticleList.ascx"), ISetValue) 
'找到DataList控件的目录主键 
objArticle.Catalog_nbr = Me.DataListCatalog.DataKeys(e.Item.ItemIndex) 
objArticle.Top = 2 
'为用户控件赋值。 
objuc.SetValue(objArticle.GetArticalTopByCatalog()) 
'加载用户控件。 
ctllaceHolder.Controls.Add(objuc) 
End If 
End If 
End Sub 