TreeView Style Modifiers

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Introduction

This is my first article posting in this site. The code snippets illustrated here will be help to customize your TreeView control in VB.NET. Here, I have tried out two things that can be done when selecting a node - first to blink the node with the help of a Timer control, and second, sort the node with its subtree nodes.

Concept

While we are working with most VB.NET controls, it is very easy to provide a good and easy-to-use presentation. But if we are working on a control like TreeView, we may face some difficulties. To overcome those issues, these code snippets will be helpful in a big way. Here, I like to focus on two things, one is how a Timer control is used and is used separately in another class for more flexibility, and how an individual node can be blinked.

Using the code

Create a new form and add a TreeView control. Apply these initial settings for the TreeView control and the Button controls in the form:

'
'TreeView_C
'
Me.TreeView_C.ImageIndex = -1
Me.TreeView_C.Location = New System.Drawing.Point(10, 10)
Me.TreeView_C.Name = "TreeView_C"
Me.TreeView_C.Nodes.AddRange(New System.Windows.Forms.TreeNode() _
  {New System.Windows.Forms.TreeNode("Root Node", _
   New System.Windows.Forms.TreeNode() _
  {New System.Windows.Forms.TreeNode("Fruits", _
   New System.Windows.Forms.TreeNode() _
  {New System.Windows.Forms.TreeNode("Apple"), _
   New System.Windows.Forms.TreeNode("Orange"), _
   New System.Windows.Forms.TreeNode("Pineapple"), _
   New System.Windows.Forms.TreeNode("Grapes")}), _
   New System.Windows.Forms.TreeNode("Animals", _
   New System.Windows.Forms.TreeNode() _
  {New System.Windows.Forms.TreeNode("Lion"), _
   New System.Windows.Forms.TreeNode("Tiger")})})})
Me.TreeView_C.SelectedImageIndex = -1
Me.TreeView_C.Size = New System.Drawing.Size(240, 250)
Me.TreeView_C.TabIndex = 0
'
'btnApplyColors
'
Me.btnApplyColors.Location = New System.Drawing.Point(10, 265)
Me.btnApplyColors.Name = "btnApplyColors"
Me.btnApplyColors.Size = New System.Drawing.Size(80, 30)
Me.btnApplyColors.TabIndex = 1
Me.btnApplyColors.Text = "Apply Colors"
'
'btnSort
'
Me.btnSort.Location = New System.Drawing.Point(175, 265)
Me.btnSort.Name = "btnSort"
Me.btnSort.Size = New System.Drawing.Size(70, 30)
Me.btnSort.TabIndex = 2
Me.btnSort.Text = "Sort"
'
'btnBlinking
'
Me.btnBlinking.Location = New System.Drawing.Point(90, 265)
Me.btnBlinking.Name = "btnBlinking"
Me.btnBlinking.Size = New System.Drawing.Size(80, 30)
Me.btnBlinking.TabIndex = 3
Me.btnBlinking.Text = "Blinking"

The code below is used to control events:

Dim sortedAsc As Boolean = False
Dim BlinkingNodes As String = ""
Dim cnode As New TreeNode
Public Enum SortOrder
    Ascending
    Descending
End Enum

Private Sub btnApplyColors_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles btnApplyColors.Click
    TreeView_C.SelectedNode.ForeColor = Color.Pink
End Sub

Private Sub btnSort_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles btnSort.Click
    TreeView_C.SelectedNode.ForeColor = _
               TreeView_C.DefaultForeColor
    cnode = TreeView_C.SelectedNode
    If sortedAsc = False Then
        SortNode(SortOrder.Ascending)
        sortedAsc = True
    Else
        SortNode(SortOrder.Descending)
        sortedAsc = False
    End If
End Sub
Private Sub btnBlinking_Click(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles btnBlinking.Click
    If BlinkingNodes.IndexOf(TreeView_C.SelectedNode.Text) < 0 Then
        Dim obj As New BlinkTimer
        obj.cnode = TreeView_C.SelectedNode
        obj.cnode.ForeColor = TreeView_C.DefaultForeColor
        obj.timer_c.Start()
        BlinkingNodes = BlinkingNodes & ", _
                        " & TreeView_C.SelectedNode.Text
    End If
End Sub

The sample function below sorts its subtree nodes on the selected base nodes:

Public Function SortNode(ByVal so As SortOrder)
    Dim retTreenode As New TreeNode
    Dim sSortString As String()
    Dim iLoop, jLoop As Integer
    ReDim sSortString(cnode.GetNodeCount(False) - 1)
    retTreenode= cnode.Clone
    For iLoop= 0 To sSortString.Length - 1
        sSortString(iLoop) = cnode.Nodes(iLoop).Text
    Next
    If so = SortOrder.Ascending Then
        sSortString.Sort(sSortString)
    Else
        sSortString.Reverse(sSortString)
    End If
    For iLoop= cnode.GetNodeCount(False) - 1 To 0 Step -1
        cnode.Nodes(iLoop).Remove()
    Next
    For jLoop= 0 To sSortString.Length - 1
        For iLoop= 0 To retTreenode.GetNodeCount(False) - 1
            If sSortString(jLoop).Trim = _
                    retTreenode.Nodes(iLoop).Text Then
                retTreenode.Nodes(iLoop).ForeColor = _
                      TreeView_C.DefaultForeColor
                cnode.Nodes.Add(retTreenode.Nodes(iLoop))

            End If
        Next
    Next
End Function

The sample class below is used internally to blink a selected node:

Public Class BlinkTimer
    Public cnode As TreeNode
    Public timer_c As New timer
    Dim BlinkColor As Color = Color.DeepPink
    Public Sub New()
        AddHandler timer_c.Tick, AddressOf BlinkOn
    End Sub
    Public Sub BlinkOn(ByVal sender As System.Object, _
                       ByVal e As System.EventArgs)
        If cnode.ForeColor.ToString <> BlinkColor.ToString _
                 And cnode.ForeColor.ToString <> _
                 Color.Transparent.ToString Then
            cnode.ForeColor = Color.Transparent
        End If
        If cnode.ForeColor.ToString = Color.Transparent.ToString _
                 Or cnode.ForeColor.ToString = _
                 Color.Empty.ToString Then
            cnode.ForeColor = BlinkColor
        ElseIf cnode.ForeColor.ToString = _
               BlinkColor.ToString Then
            cnode.ForeColor = Color.Transparent
        End If
    End Sub
End Class

Points of Interest

On working with the Timer control, it is better to assign a Timer control in a separate class and access it, instead of assigning it to a control, since the Timer control can be accessed with a single instance and used multiple times.