Sử dụng Datalist lồng nhau (Nested Datalist) trong Asp.net

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(Nested datalist in Asp.net) – Đối với các trang tin tức hoặc thương mại điện tử, việc sử dụng các Datalist lồng nhau thường xuyên được sử dụng. Việc sử dụng này giúp người lập trình hiển thị danh sách các chuyên mục và các bài viết trong từng chuyên mục. Bài viết dưới đây sẽ hướng dẫn các bạn cách sử dụng 2 Datalist lồng nhau, Datalist đầu sẽ hiển thị danh sách Loại và Datalist thứ 2 sẽ hiển thị danh sách sản phẩm của từng loại.

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- B1: Download CSDL Northwind tại đây và thực hiện công việc Restore Data.

- B2: Tạo Project trong Microsoft Visual Studio 2010

Trong Visual Studio tạo 1 Class có tên: Utility và nhập đoạn Code phía dưới cho Class này.

C# Code

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Data.SqlClient;

using System.Data;

using System.Configuration;

namespace NestedDataList

{

public class SqlDataProvider

{

#region "Membres Prives"

private string _connectionString;

#endregion

#region "Constructeurs"

public SqlDataProvider()

{

try

{

_connectionString = ConfigurationManager.ConnectionStrings["SiteSqlServer"].ConnectionString;

}

catch

{

}

#endregion

#region "Proprietes"

public string ConnectionString

{

get { return _connectionString; }

}

#endregion

#region "Functions"

public DataTable FillTable(string sql)

{

try

{

DataTable tb = new DataTable();

SqlDataAdapter adap = new SqlDataAdapter(sql, _connectionString);

adap.Fill(tb);

return tb;

}

catch

{

return null;

}

#endregion

}

VB.NET Code

Imports System.Data.SqlClient

Imports System.Data

Namespace NestedDataList

Public Class SqlDataProvider

#Region "Membres Prives"

Shared _IsError As Boolean = False

Private _connectionString As String

#End Region

#Region "Constructeurs"

Public Sub New()

Try

_connectionString = ConfigurationManager.ConnectionStrings("SiteSqlServer").ConnectionString

_IsError = False

Catch ex As Exception

_IsError = True

End Try

End Sub

#End Region

#Region "Proprietes"

Public ReadOnly Property ConnectionString() As String

Get

Return _connectionString

End Get

End Property

#End Region

#Region "Functions"

Public Function FillTable(ByVal sql As String) As DataTable

Try

Dim tb As New DataTable

Dim adap As New SqlDataAdapter(sql, _connectionString)

adap.Fill(tb)

Return tb

Catch ex As Exception

Return Nothing

End Try

End Function

#End Region

End Class

End Namespace

Chú ý: Thuộc tính SiteSqlServer chính là chuỗi Connect với SQL Server trong file Web.Config

- B3: Mở file Default.aspx dưới dạng HTML và nhập mã HTML
C#

<%@ Page Title="Nested DataList in ASP.NET" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="NestedDataList._Default" %>

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

<asp:ScriptManager ID="ScriptManager1" runat="server">

</asp:ScriptManager>

<h3>

Nested DataList in ASP.NET

</h3>

<br />

<asp:UpdatePanel ID="updatePanel" runat="server" UpdateMode="Conditional">

<tr>

<td>

<asp:datalist id="lstCategory" runat="server" cellspacing="0" cellpadding="0" Width="100%" OnItemDataBound="lstCategory_ItemDataBound">

<tr>

<td>

<asp:Label CssClass="Category" id="lblCategory" runat="server" text='<%# Eval("CategoryName")%>'>

</asp:Label>

</td>

</tr>

</table>

<asp:DataList ID="lstProduct" OnItemDataBound="Detail_Bound" runat="server" CellPadding="0" CellSpacing="0" Width="100%" RepeatDirection="Horizontal" RepeatColumns="5">

<tr>

<asp:HyperLink id="lnkProductImage" runat="server" CssClass="Image">

<asp:Image id="imgProductImage" runat="server" ImageAlign="Middle" Height="120px" Width="120px" hspace="0" vspace="0"></asp:Image>

</asp:HyperLink>

</td>

</tr>

<tr>

<asp:HyperLink ID="lnkProductName" CssClass="Title" runat="server">

</asp:HyperLink>

</td>

</tr>

</table>

</ItemTemplate>

</asp:DataList>

</ItemTemplate>

</asp:datalist>

</td>

</tr>

</table>

</ContentTemplate>

</asp:UpdatePanel>

</asp:Content>

VB.Net Code

<%@ Page Title="Nested DataList in ASP.NET" Language="vb" MasterPageFile="~/Site.Master" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="NestedDataList._Default" %>

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

<asp:ScriptManager ID="ScriptManager1" runat="server">

</asp:ScriptManager>

<h3>

Nested DataList in ASP.NET

</h3>

<br />

<asp:UpdatePanel ID="updatePanel" runat="server" UpdateMode="Conditional">

<tr>

<td>

<asp:datalist id="lstCategory" runat="server" cellspacing="0" cellpadding="0" Width="100%">

<tr>

<td>

<asp:Label CssClass="Category" id="lblCategory" runat="server" text='<%# Eval("CategoryName")%>'>

</asp:Label>

</td>

</tr>

</table>

<asp:DataList ID="lstProduct" OnItemDataBound="Detail_Bound" runat="server" CellPadding="0" CellSpacing="0" Width="100%" RepeatDirection="Horizontal" RepeatColumns="5">

<tr>

<asp:HyperLink id="lnkProductImage" runat="server" CssClass="Image">

<asp:Image id="imgProductImage" runat="server" ImageAlign="Middle" Height="120px" Width="120px" hspace="0" vspace="0"></asp:Image>

</asp:HyperLink>

</td>

</tr>

<tr>

<asp:HyperLink ID="lnkProductName" CssClass="Title" runat="server">

</asp:HyperLink>

</td>

</tr>

</table>

</ItemTemplate>

</asp:DataList>

</ItemTemplate>

</asp:datalist>

</td>

</tr>

</table>

</ContentTemplate>

</asp:UpdatePanel>

</asp:Content>

- B4: Viết Code cho file Default.aspx

C#

//Visit http://www.laptrinhdotnet.com for more ASP.NET Tutorials

using Microsoft.VisualBasic;

using System;

using System.Collections;

using System.Collections.Generic;

using System.Data;

using System.Diagnostics;

using System.Web.UI;

using System.Web.UI.WebControls;

namespace NestedDataList

{

public partial class _Default : System.Web.UI.Page

{

#region "Bind Data"

private void BindCategories()

{

DataTable objBind = new DataTable();

objBind = BindData();

if (objBind != null)

{

if (objBind.Rows.Count > 0)

{

lstCategory.DataSource = objBind;

lstCategory.DataBind();

lstCategory.Visible = true;

updatePanel.Update();

}

else

{

lstCategory.Visible = false;

}

private DataTable BindData()

{

SqlDataProvider objSQL = new SqlDataProvider();

DataTable objBind = objSQL.FillTable("Select Categories.* From Categories");

return objBind;

}

private DataTable BindProduct(int CategoryID)

{

SqlDataProvider objSQL = new SqlDataProvider();

DataTable objBind = objSQL.FillTable("Select top 5 Products.* From Products Where CategoryID=" + CategoryID + "");

return objBind;

}

#endregion

#region "Datalist Methods"

protected void lstCategory_ItemDataBound(object sender, System.Web.UI.WebControls.DataListItemEventArgs e)

{

if (e.Item.ItemType == ListItemType.Item | e.Item.ItemType == ListItemType.AlternatingItem)

{

int CategoryID = Convert.ToInt32(DataBinder.Eval(e.Item.DataItem, "CategoryID"));

DataTable objBind = new DataTable();

objBind = BindProduct(CategoryID);

if (objBind.Rows.Count != 0)

{

DataList lstDetail = (DataList)e.Item.FindControl("lstProduct");

if (lstDetail != null)

{

lstDetail.DataSource = objBind;

lstDetail.DataBind();

}

public void Detail_Bound(object sender, DataListItemEventArgs e)

{

if (e.Item.ItemType == ListItemType.Item | e.Item.ItemType == ListItemType.AlternatingItem)

{

int ProductID = Convert.ToInt32(DataBinder.Eval(e.Item.DataItem, "ProductID"));

string ProductName = DataBinder.Eval(e.Item.DataItem, "ProductName").ToString();

HyperLink lnkProductName = (HyperLink)e.Item.FindControl("lnkProductName");

if (lnkProductName != null)

{

lnkProductName.Text = ProductName;

lnkProductName.NavigateUrl = "Default.aspx";

}

HyperLink lnkProductImage = (HyperLink)e.Item.FindControl("lnkProductImage");

if (lnkProductImage != null)

{

Image imgArticleImage = (Image)lnkProductImage.FindControl("imgProductImage");

if (imgArticleImage != null)

{

imgArticleImage.ImageUrl = Page.ResolveUrl("Images/no_image.jpg");

imgArticleImage.ImageAlign = ImageAlign.AbsMiddle;

}

#endregion

#region "Event Handles"

protected void Page_Load(object sender, System.EventArgs e)

{

try

{

if (!IsPostBack)

{

BindCategories();

}

catch

{

}

#endregion

}

VB.NET Code

'Visit http://www.laptrinhdotnet.com for more ASP.NET Tutorials

Namespace NestedDataList

Public Class _Default

Inherits System.Web.UI.Page

#Region "Bind Data"

Private Sub BindCategories()

Dim objBind As New DataTable

objBind = BindData()

If Not objBind Is Nothing Then

If objBind.Rows.Count > 0 Then

lstCategory.DataSource = objBind

lstCategory.DataBind()

lstCategory.Visible = True

updatePanel.Update()

Else

lstCategory.Visible = False

End If

End Sub

Private Function BindData() As DataTable

Dim objSQL As New SqlDataProvider

Dim objBind As DataTable = objSQL.FillTable("Select Categories.* From Categories")

Return objBind

End Function

Private Function BindProduct(ByVal CategoryID As Integer) As DataTable

Dim objSQL As New SqlDataProvider

Dim objBind As DataTable = objSQL.FillTable("Select top 5 Products.* From Products Where CategoryID=" & CategoryID & "")

Return objBind

End Function

#End Region

#Region "Datalist Methods"

Private Sub lstCategory_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataListItemEventArgs) Handles lstCategory.ItemDataBound

If (e.Item.ItemType = ListItemType.Item Or e.Item.ItemType = ListItemType.AlternatingItem) Then

Dim CategoryID As Integer = DataBinder.Eval(e.Item.DataItem, "CategoryID")

Dim objBind As New DataTable

objBind = BindProduct(CategoryID)

If objBind.Rows.Count <> 0 Then

Dim lstDetail As DataList = DirectCast(e.Item.FindControl("lstProduct"), DataList)

If Not lstDetail Is Nothing Then

lstDetail.DataSource = objBind

lstDetail.DataBind()

End If

End Sub

Public Sub Detail_Bound(ByVal sender As Object, ByVal e As DataListItemEventArgs)

Try

If (e.Item.ItemType = ListItemType.Item Or e.Item.ItemType = ListItemType.AlternatingItem) Then

Dim ProductID As Integer = DataBinder.Eval(e.Item.DataItem, "ProductID")

Dim ProductName As String = DataBinder.Eval(e.Item.DataItem, "ProductName")

Dim lnkProductName As HyperLink = DirectCast(e.Item.FindControl("lnkProductName"), HyperLink)

If Not lnkProductName Is Nothing Then

lnkProductName.Text = ProductName

lnkProductName.NavigateUrl = "Default.aspx"

End If

Dim lnkProductImage As HyperLink = DirectCast(e.Item.FindControl("lnkProductImage"), HyperLink)

If Not lnkProductImage Is Nothing Then

Dim imgArticleImage As Image = DirectCast(lnkProductImage.FindControl("imgProductImage"), Image)

If Not imgArticleImage Is Nothing Then

imgArticleImage.ImageUrl = Page.ResolveUrl("Images/no_image.jpg")

imgArticleImage.ImageAlign = ImageAlign.AbsMiddle

End If

Catch exception As Exception

End Try

End Sub

#End Region

#Region "Event Handles"

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

Try

If Page.IsPostBack = False Then

BindCategories()

End If

Catch ex As Exception

End Try

End Sub

#End Region

End Class

End Namespace

Bây giờ chạy Project chương trình sẽ hiển thị danh sách các Category và ứng với mỗi Category là danh sách các Product nằm trong nó.

Chúc các bạn thành công!

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