This tutorial will show how we can create a relational hierarchical structure using nested repeaters. This is useful for such an implementation as a structured menu system with different levels (categories and sub-categories). VB version.
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Repeaters are very powerful tools for displaying data, and while they are not the most feature-packed tool in the ASP.NET toolbox, they are arguably the most versatile.
One of the things we can do with Repeaters is nest them to show hierarchical data. In this example, we will display a menu system with sub-menu items, using two Repeaters. These menu items will be pulled from a Sample database.
First, we add the Connection String in Web.config:
| <appSettings>
<add key="ConnectionString" value="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True" />
</appSettings> <connectionStrings/> |
We also need the following assembly references:
Imports System.Data
Imports System.Data.SqlClient |
We add the code for the two nested Repeater Controls:
<form id="form1" runat="server">
<asp:Repeater ID="repMenu1" runat="server">
<ItemTemplate>
<a href="#"><%#DataBinder.Eval(Container.DataItem, "menuItem")%></a> <asp:Repeater ID="repMenu2" runat="server">
<HeaderTemplate><br /></HeaderTemplate> <ItemTemplate><div style="margin-left:15px;"><a href="#"><%#DataBinder.Eval(Container.DataItem, "subMenuItem")%></a><br /></div></ItemTemplate> </asp:Repeater> </ItemTemplate>
</form> |
Notice the nested Repeater is in the <ItemTemplate> tags of the first.
Next, we add the following to the code-behind.
| Protected Sub ShowMenu()
Dim cmd As New SqlDataAdapter("SELECT * FROM [Table1];SELECT * FROM [Table2]", New SqlConnection(ConfigurationManager.AppSettings("ConnectionString")))
Dim ds As New DataSet()
cmd.Fill(ds)
ds.Relations.Add(New DataRelation("nestThem", ds.Tables(0).Columns("ID"), ds.Tables(1).Columns("parentMenuID")))
repMenu1.DataSource = ds
repMenu1.DataBind() End Sub
Protected Sub repMenu1_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles repMenu1.ItemDataBound
Dim dv As DataRowView = TryCast(e.Item.DataItem, DataRowView) If dv IsNot Nothing Then
Dim repSubMenu As Repeater = TryCast(e.Item.FindControl("repMenu2"), Repeater) If repSubMenu IsNot Nothing Then
repSubMenu.DataSource = dv.CreateChildView("nestThem")
repSubMenu.DataBind() End If End If |
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The above method should be called on Page_Load so that it can bind the data to the first repeater, which will retrieve the top-menu items from the database and populate the repeater. When menu1 is databound, it will find the matching submenu items in the database and bind them to the second (nested) repeater, displaying the sub-menu items below the parent.
The entire code-behind should look something like this:
Imports System.Data
Imports System.Data.SqlClient
Partial Class _Default
Inherits System.Web.UI.Page Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
ShowMenu() End Sub Protected Sub ShowMenu()
Dim cmd As New SqlDataAdapter("SELECT * FROM [Table1];SELECT * FROM [Table2]", New SqlConnection(ConfigurationManager.AppSettings("ConnectionString")))
Dim ds As New DataSet()
cmd.Fill(ds)
ds.Relations.Add(New DataRelation("nestThem", ds.Tables(0).Columns("ID"), ds.Tables(1).Columns("parentMenuID")))
repMenu1.DataSource = ds
repMenu1.DataBind() End Sub Protected Sub repMenu1_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles repMenu1.ItemDataBound
Dim dv As DataRowView = TryCast(e.Item.DataItem, DataRowView) If dv IsNot Nothing Then
Dim repSubMenu As Repeater = TryCast(e.Item.FindControl("repMenu2"), Repeater) If repSubMenu IsNot Nothing Then
repSubMenu.DataSource = dv.CreateChildView("nestThem")
repSubMenu.DataBind() End If End If End Sub |
Looking for the C#.NET 2005 Version? Click Here!
Looking for more ASP.NET Tutorials? Click Here!
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