VB.Net Dynamic Recursive Menu

**jmurrayhead** · jmurrayhead, March 18th, 2008 11:47 AM

I got this idea from helping another member with some similar code. This uses the Menu Class to build a menu a populates it from a database, allowing for multiple child menus. Sample files are included.
Menu.aspx

Code:

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="menu.aspx.vb" Inherits="_Menu"%>
<html>
<head>
    <title>Recursive Menu Example</title>
</head>
    <body>
        <form id="Form1" runat="server">
            <asp:Panel ID="Panel1" runat="server" />
        </form>
    </body>
</html>

menu.aspx.vb

Code:

Imports System.Data.OleDb
Partial Class _Menu
    Inherits System.Web.UI.Page
    '//Connection to database from web.config file
    Private conn As New OleDbConnection(ConfigurationManager.ConnectionStrings("menu").ConnectionString)
    Private Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
        Call PopulateMenu()
    End Sub
    Private Sub PopulateMenu()
        Try
            '//Define new menu
            Dim menu As New Menu()
            '//Retrieve menu data
            Dim menuData As DataTable = GetMenuData()
            AddTopMenuItems(menuData, menu)
            Me.Panel1.Controls.Add(menu)
            Me.Panel1.DataBind()
        Catch ex As Exception
            Response.Write(ex.Message.ToString() & "<br />")
        End Try
    End Sub
    Private Function GetMenuData() As DataTable
        Try
            '//Populate DataTable
            Dim strSQL As String = "SELECT * FROM tbl_menu"
            Dim datMenu As OleDbDataAdapter = New OleDbDataAdapter(strSQL, conn)
            Dim tblMenu As DataTable = New DataTable()
            datMenu.Fill(tblMenu)
            Return tblMenu
        Catch ex As Exception
            Response.Write(ex.Message.ToString() & "<br />")
        End Try        
    End Function
    Private Sub AddTopMenuItems(ByVal menuData As DataTable, ByVal menu As Menu)
        Try
            '//Populate DataView
            Dim datView As DataView = New DataView(menuData)
            '//Filter parent menu items
            datView.RowFilter = "parentid = 0"
            '//Populate menu with top menu items
            Dim datRow As DataRowView
            For Each datRow In datView
                '//Define new menu item
                Dim parentMenu As MenuItem
                parentMenu = CreateMenuItem(datRow("linktext"), datRow("linkurl"), datRow("linktext"))
                menu.Items.Add(parentMenu)
                '//Populate child items of this parent
                AddChildMenuItems(menuData, datRow("itemid"), parentMenu)
            Next
        Catch ex As Exception
            Response.Write(ex.Message.ToString() & "<br />")
        End Try
    End Sub
    Private Sub AddChildMenuItems(ByVal menuData As DataTable, ByVal parentID As Integer, Byval parentMenu As MenuItem)
        Try
            '//Populate DataView
            Dim datView As DataView = New DataView(menuData)
 
            '//Filter child menu items
            datView.RowFilter = "parentid = " & parentID
            '//Populate parent menu item with child menu items
            Dim datRow As DataRowView
            For Each datRow in datView
                '//Define new menu item
                Dim childMenu As MenuItem
                childMenu = CreateMenuItem(datRow("linktext"), datRow("linkurl"), datRow("linktext"))
                parentMenu.ChildItems.Add(childMenu)
                '//Populate child items of this parent
                AddChildMenuItems(menuData, datRow("itemid"), childMenu)
            Next
        Catch ex As Exception
            Response.Write(ex.Message.ToString() & "<br />")
        End Try
    End Sub
    Private Function CreateMenuItem(ByVal strText As String, ByVal strUrl As String, ByVal strToolTip As String) As MenuItem
        Try
            '//Create new menu item
            Dim menuItem As New menuItem()
            '//Set properties of the menu item
            With menuItem
                .Text = strText
                .NavigateUrl = strUrl
                .ToolTip = strToolTip
            End With
            Return menuItem
        Catch ex As Exception
            Response.Write(ex.Message.ToString() & "<br />")
        End Try        
    End Function
End Class

Untested C# - I haven't tested this as I'm not a C# coder...if anyone has any issues with this, let me know:

Code:

using System.Data.OleDb;
partial class _Menu : System.Web.UI.Page
{
    ////Connection to database from web.config file
    private OleDbConnection conn = new OleDbConnection(ConfigurationManager.ConnectionStrings("menu").ConnectionString);
    private void Page_Load(object sender, EventArgs e)
    {
        PopulateMenu();
    }
    private void PopulateMenu()
    {
        try {
            ////Define new menu
            Menu menu = new Menu();
            ////Retrieve menu data
            DataTable menuData = GetMenuData();
            AddTopMenuItems(menuData, menu);
            this.Panel1.Controls.Add(menu);
            this.Panel1.DataBind();
        }
        catch (Exception ex) {
            Response.Write(ex.Message.ToString() + "<br />");
        }
    }
    private DataTable GetMenuData()
    {
        try {
            ////Populate DataTable
            string strSQL = "SELECT * FROM tbl_menu";
            OleDbDataAdapter datMenu = new OleDbDataAdapter(strSQL, conn);
            DataTable tblMenu = new DataTable();
            datMenu.Fill(tblMenu);
            return tblMenu;
        }
        catch (Exception ex) {
            Response.Write(ex.Message.ToString() + "<br />");
        }
    }
    private void AddTopMenuItems(DataTable menuData, Menu menu)
    {
        try {
            ////Populate DataView
            DataView datView = new DataView(menuData);
            ////Filter parent menu items
            datView.RowFilter = "parentid = 0";
            ////Populate menu with top menu items
            DataRowView datRow = default(DataRowView);
            foreach ( datRow in datView) {
                ////Define new menu item
                MenuItem parentMenu = default(MenuItem);
                parentMenu = CreateMenuItem(datRow("linktext"), datRow("linkurl"), datRow("linktext"));
                menu.Items.Add(parentMenu);
                ////Populate child items of this parent
                AddChildMenuItems(menuData, datRow("itemid"), parentMenu);
            }
        }
        catch (Exception ex) {
            Response.Write(ex.Message.ToString() + "<br />");
        }
    }
    private void AddChildMenuItems(DataTable menuData, int parentID, MenuItem parentMenu)
    {
        try {
            ////Populate DataView
            DataView datView = new DataView(menuData);
            
            ////Filter child menu items
            datView.RowFilter = "parentid = " + parentID;
            ////Populate parent menu item with child menu items
            DataRowView datRow = default(DataRowView);
            foreach ( datRow in datView) {
                ////Define new menu item
                MenuItem childMenu = default(MenuItem);
                childMenu = CreateMenuItem(datRow("linktext"), datRow("linkurl"), datRow("linktext"));
                parentMenu.ChildItems.Add(childMenu);
                ////Populate child items of this parent
                AddChildMenuItems(menuData, datRow("itemid"), childMenu);
            }
        }
        catch (Exception ex) {
            Response.Write(ex.Message.ToString() + "<br />");
        }
    }
    private MenuItem CreateMenuItem(string strText, string strUrl, string strToolTip)
    {
        try {
            ////Create new menu item
            menuItem menuItem = new menuItem();
            ////Set properties of the menu item
            {
                menuItem.Text = strText;
                menuItem.NavigateUrl = strUrl;
                menuItem.ToolTip = strToolTip;
            }
            return menuItem;
        }
        catch (Exception ex) {
            Response.Write(ex.Message.ToString() + "<br />");
        }
    }
}

Table design:
This setup uses a table with the following field types:
itemid - AutoNumber
parentid - Number
linktext - Text
linkurl - Text
Parent items will have parentid = 0 whereas child items will have parentid = itemid of the parent.

**yiffzer** · yiffzer, February 15th, 2010 01:50 PM

I tried testing this in VS2008 but had errors. Nothing worked. This seemed to be my last hope of solving this complex dynamic navigation list.

I'm at loss, really.

**jmurrayhead** · jmurrayhead, February 15th, 2010 02:15 PM

Did you receive any error messages?

**yiffzer** · yiffzer, February 15th, 2010 02:21 PM

Before even running it, a bunch of warnings/errors came up:

**jmurrayhead** · jmurrayhead, February 15th, 2010 02:26 PM

If using VB, add this to the top of the page:

Code:

Imports System.Data

If using C#, add this to the top:

Code:

using System.Data;

**tomhawk** · tomhawk, May 16th, 2010 08:57 PM

Thanks alot

**Wolffy** · Wolffy, May 17th, 2010 05:39 PM

The reason for the warnings you are getting is that if the CreateMenuItem (for example) fails and throws and exception, no return statement is being executed. However, in looking at this method, I wonder about the necessity of adding the overhead of exception handling since the only thing it is doing is instantiating a MenuItem and setting some properties. The method consumes the exception and thus the calling method would have no way of knowing that the CreateMenuItem failed -- and it would happily continue on and throw a NullReferenceException at some point. Personally I would remove the try..catch block from CreateMenuItem because (1) this is a private method and thus it won't be used by developers; we can handle the errors within the class and (2) it is very unlikely that it would throw an exception, given the instructions being executed.

If you really want to handle the exception here to generate the error message as some HTML (as in the example), that's fine -- however I would either then rethrow the exception or place a return null (or return nothing) statement outside the try...catch block and then check for a null in the calling method. Rethrowing the exception is valid since the exception is not handled in a way that would allow execution to continue and thus could/should be handled higher up in the stack.

**jmurrayhead** · jmurrayhead, June 30th, 2010 05:57 PM

I admit that this isn't the best error handling as I wrote this a few years ago...but there isn't any overhead of using Try...Catch unless there is actually an exception.

When I have spare time, I plan on improving the coding method and making this a server control, where people can simply add reference to the dll and use it like any other control.

**Wolffy** · Wolffy, July 1st, 2010 09:28 AM

I'm going to conditionally disagree in that Try...Catch does add overhead in setting up the exception stack -- however, I make it conditional until I get my computer here (oh when..oh when) and can look at the MSIL being generated.

**jmurrayhead** · jmurrayhead, July 1st, 2010 09:32 AM

Quote from MSDN:

Finding and designing away exception-heavy code can result in a decent perf win. Bear in mind that this has nothing to do with try/catch blocks: you only incur the cost when the actual exception is thrown. You can use as many try/catch blocks as you want. Using exceptions gratuitously is where you lose performance. For example, you should stay away from things like using exceptions for control flow.

Performance Tips and Tricks in .NET Applications

unless I'm misunderstanding something here?

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