使用递归从数据库读取数据来动态建立菜单

表结构与内容

MenBh            MenText     Bhparent

0001             文件         

0002             编辑         

0005             打开          0001

0006             新建          0001

0011             access数据库  0006

0012             VFP的Dbf      0006

0013             剪切          0002

0014             复制          0002

0015            完全复制       0014

    

Private m As New MainMenu()

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        Dim conn As New SqlConnection("server=localhost;uid=sa;pwd=;database=jiang")

        Dim cmd As New SqlCommand("select * from a_menu ", conn)

        Dim ds As New DataSet()

        Dim sqldpr As New SqlDataAdapter(cmd)

        sqldpr.Fill(ds, "menu")

        Me.DataGrid1.DataSource = ds.Tables("menu")

        '创建关系

        Dim dr As New DataRelation("self_menu", ds.Tables("menu").Columns("MenBh"), ds.Tables("menu").Columns("Bhparent"))

        ds.Relations.Add(dr)

        Dim r1 As DataRow

        '查找最高的菜单级别,也就是Bhparent列为空的行

        For Each r1 In ds.Tables("menu").Rows

            If r1.IsNull("Bhparent") Then

                addmenuitem(r1, Nothing)

            End If

        Next

        Me.Menu = m '指定主窗体菜单

    End Sub

    '递归函数

    Private Sub addmenuitem(ByVal r As DataRow, ByVal item As MenuItem)

        Dim mi As MenuItem

        '如果是最外层菜单，要直接添加

        If item Is Nothing Then

            mi = m.MenuItems.Add(r.Item("MenText"))

        Else '如果是下级菜单要在菜单项的上级添加

            mi = item.MenuItems.Add(r.Item("MenText"))

        End If

        Dim r2 As DataRow

        For Each r2 In r.GetChildRows("self_menu")

            addmenuitem(r2, mi)

        Next

    End Sub

'--------------------------------------------------------一种方法的改进

‘/////////////////////////////////////////////////////////////////////////////////////

‘继承自menuitem的类

‘/////////////////////////////////////////////////////////////////////////////////////

Public Class mymenuitem

Inherits System.Windows.Forms.MenuItem

 

Public Sub New(ByVal s As String, ByVal tag As String)

        MyBase.New()

        Me.Text = s

        m_tag = tag

    End Sub

    Private m_tag As String

    Public Property tag() As String

        Get

            Return m_tag

        End Get

        Set(ByVal Value As String)

            m_tag = Value

        End Set

End Property

  End class

‘////////////////////////////////////////////////////////////////////////////////////

‘在代码中实现这种菜单项的添加和菜单的建立

‘//////////////////////////////////////////////////////////////////////////////////

Private m As New MainMenu()

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        Dim conn As New SqlConnection("server=localhost;uid=sa;pwd=;database=jiang")

        Dim cmd As New SqlCommand("select * from a_menu ", conn)

        Dim ds As New DataSet()

        Dim sqldpr As New SqlDataAdapter(cmd)

        sqldpr.Fill(ds, "menu")

 

 

        'Me.DataGrid1.DataSource = ds.Tables("menu")

        Me.DataGrid1.DataSource = ds

        Me.DataGrid1.DataMember = "menu"

        '创建关系

        Dim dr As New DataRelation("self_menu", ds.Tables("menu").Columns("MenBh"), ds.Tables("menu").Columns("Bhparent"))

        ds.Relations.Add(dr)

        Dim r1 As DataRow

 

        '查找最高的菜单级别,也就是Bhparent列为空的行

        For Each r1 In ds.Tables("menu").Rows

            If r1.IsNull("Bhparent") Then

                addmenuitem(r1, Nothing)

            End If

        Next

        Me.Menu = m '指定主窗体菜单

    End Sub

    '递归函数

    Private Sub addmenuitem(ByVal r As DataRow, ByVal item As MenuItem)

        Dim mi As MenuItem

 

        '如果是最外层菜单，要直接添加

        If item Is Nothing Then

            Try

                mi = New mymenuitem(r.Item("MenText"), "1")

                m.MenuItems.Add(mi)

            Catch ex As Exception

                MessageBox.Show(ex.ToString)

            End Try

        Else '如果是下级菜单要在菜单项的上级添加

            mi = New mymenuitem(r.Item("MenText"), "2")

            item.MenuItems.Add(mi)

        End If

        Dim r2 As DataRow

        For Each r2 In r.GetChildRows("self_menu")

            addmenuitem(r2, mi)

        Next

    End Sub