Question

I extended treeview, treenode, and nodetype so I could have custom nodes. Certain nodes have image buttons on them allowing them to add a child node or delete the node. I can’t handle any of the events from my buttons.

Public Class ContentTreeView
Inherits TreeView

Public Event OnAddChild(ByVal sender As Object, ByVal e As EventArgs)
Public Event OnDelete(ByVal sender As Object, ByVal e As EventArgs)

Private _AddImageURL As String = String.Empty
Private _DeleteImageURL As String = String.Empty

Public Property AddImageURL() As String
    Get
        Return _AddImageURL
    End Get
    Set(ByVal value As String)
        _AddImageURL = value
    End Set
End Property

Public Property DeleteImageURL() As String
    Get
        Return _DeleteImageURL
    End Get
    Set(ByVal value As String)
        _DeleteImageURL = value
    End Set
End Property

Protected Overrides Function CreateNode() As TreeNode
    Dim retval As ContentTreeNode = New ContentTreeNode(AddImageURL, DeleteImageURL)
    AddHandler retval.OnAddChild, AddressOf ContentNode_AddChild
    AddHandler retval.OnDelete, AddressOf ContentNode_Delete
    Return retval
End Function

Protected Sub ContentNode_AddChild(ByVal sender As Object, ByVal e As EventArgs)
    RaiseEvent OnAddChild(Nothing, Nothing)
End Sub
Protected Sub ContentNode_Delete(ByVal sender As Object, ByVal e As EventArgs)
    RaiseEvent OnDelete(Nothing, Nothing)
End Sub

Public Class ContentTreeNode
    Inherits TreeNode

    Public Event OnAddChild(ByVal sender As Object, ByVal e As EventArgs)
    Public Event OnDelete(ByVal sender As Object, ByVal e As EventArgs)

    Private _AddImageURL As String = String.Empty
    Private _DeleteImageURL As String = String.Empty

    Private btnAddChild As ImageButton
    Private btnDelete As ImageButton

    Public Sub New(ByVal AddImageURL_ As String, ByVal DeleteImageURL_ As String)
        _AddImageURL = AddImageURL_
        _DeleteImageURL = DeleteImageURL_
    End Sub

    Public Property AddImageURL() As String
        Get
            Return _AddImageURL
        End Get
        Set(ByVal value As String)
            _AddImageURL = value
        End Set
    End Property

    Public Property DeleteImageURL() As String
        Get
            Return _DeleteImageURL
        End Get
        Set(ByVal value As String)
            _DeleteImageURL = value
        End Set
    End Property

    Protected Overrides Sub RenderPreText(ByVal writer As HtmlTextWriter)
    End Sub

    Protected Overrides Sub RenderPostText(ByVal writer As HtmlTextWriter)
        CreateChildControls()
        If GetTreeNodeType() <> ContentTreeNodeTypes.Root Then
            btnAddChild.RenderControl(writer)
            If GetTreeNodeType() <> ContentTreeNodeTypes.Category Then
                btnDelete.RenderControl(writer)
            End If
        End If
    End Sub

    Private Function GetTreeNodeType() As TreeNodeTypes
        Dim leaf As TreeNodeTypes = TreeNodeTypes.Leaf
        If ((Me.Depth = 0) AndAlso (Me.ChildNodes.Count > 0)) Then
            Return ContentTreeNodeTypes.Root
        End If
        If Me.Depth = 1 Then
            Return ContentTreeNodeTypes.Category
        End If
        If ((Me.ChildNodes.Count <= 0) AndAlso Not Me.PopulateOnDemand) Then
            Return leaf
        End If
        Return ContentTreeNodeTypes.Parent
    End Function

    Protected Sub CreateChildControls()
        'Controls.Clear()

        '***Creat Add Button***
        btnAddChild = New ImageButton()
        btnAddChild.ID = "btnAddChild"
        btnAddChild.ImageUrl = AddImageURL
        btnAddChild.ToolTip = "Add Child"
        AddHandler btnAddChild.Click, AddressOf btnAddChild_Click

        '***Create DeleteButton***
        btnDelete = New ImageButton()
        btnDelete.ID = "btnDelete"
        btnDelete.ImageUrl = DeleteImageURL()
        btnDelete.ToolTip = "Delete Page"
        AddHandler btnDelete.Click, AddressOf btnDelete_Click

        ''***Add Controls***
        'Me.Controls.Add(btnAddChild)
        'Me.Controls.Add(btnDelete)
    End Sub

    Protected Sub btnAddChild_Click(ByVal sender As Object, ByVal e As EventArgs)
        RaiseEvent OnAddChild(Nothing, Nothing)
    End Sub
    Protected Sub btnDelete_Click(ByVal sender As Object, ByVal e As EventArgs)
        RaiseEvent OnDelete(Nothing, Nothing)
    End Sub


    Public Enum ContentTreeNodeTypes
        All = 7
        Leaf = 4
        None = 0
        Parent = 2
        Root = 1
        Category = 3
    End Enum
End Class

End Class

1) Can I implement something like IPostBackEventHandler?
2) Is this possible since treeNode isn’t a control/webcontrol?

Any help is appreciated… Thanks!!!

Answer 1

After reading this post. I decided to use the following solution. First I changed my CreateChildControls method to:

        Protected Sub CreateChildControls()
        Dim page As Page = HttpContext.Current.CurrentHandler
        Dim csm As ClientScriptManager = page.ClientScript
        Dim control As WebControl = page.Master.FindControl(_ContainerID).FindControl(_ContentTreeViewID)

        '***Creat Add Button***
        btnAddChild = New ImageButton()
        btnAddChild.ID = "btnAddChild"
        btnAddChild.ImageUrl = AddImageURL
        btnAddChild.ToolTip = "Add Child"            
        btnAddChild.Attributes.Add("onClick", csm.GetPostBackEventReference(control, String.Format("{0}:{1}", Me.Value, "Add")))

        '***Create DeleteButton***
        btnDelete = New ImageButton()
        btnDelete.ID = "btnDelete"
        btnDelete.ImageUrl = DeleteImageURL()
        btnDelete.ToolTip = "Delete Page"
        btnDelete.Attributes.Add("onClick", csm.GetPostBackEventReference(control, String.Format("{0}:{1}", Me.Value, "Delete")))
    End Sub

Then I had to implement IPostBackEventHandler in the custom treeview to handle the postback events. Maybe not the best solution but it works well with custom event args.