RadTreeNode.Nodes.Clear() scrolls RadTreeView to first node

[Clive]

Hi,

When using a node's Nodes.Clear() method the tree view scrolls up to the top and shows the tree view's first node.

If I load the Form2 and scroll down a bit so the first node is no longer visible, and check the check box, then double click on a node it will expand, and make the top node visible.

My work around is to remove each node individually, i.e.
If I load the Form2 and scroll down a bit so the first node is no longer visible, then double click on a node it will expand.

Public Class Form2
    Inherits System.Windows.Forms.Form

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        Try
            If disposing AndAlso components IsNot Nothing Then
                components.Dispose()
            End If
        Finally
            MyBase.Dispose(disposing)
        End Try
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.RadTreeView1 = New Telerik.WinControls.UI.RadTreeView()
        Me.CheckBox1 = New System.Windows.Forms.CheckBox()
        CType(Me.RadTreeView1, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.SuspendLayout()
        '
        'RadTreeView1
        '
        Me.RadTreeView1.BackColor = System.Drawing.SystemColors.Control
        Me.RadTreeView1.Cursor = System.Windows.Forms.Cursors.Default
        Me.RadTreeView1.Font = New System.Drawing.Font("Segoe UI", 8.25!)
        Me.RadTreeView1.ForeColor = System.Drawing.Color.Black
        Me.RadTreeView1.Location = New System.Drawing.Point(12, 11)
        Me.RadTreeView1.Name = "RadTreeView1"
        Me.RadTreeView1.RightToLeft = System.Windows.Forms.RightToLeft.No
        '
        '
        '
        Me.RadTreeView1.RootElement.ForeColor = System.Drawing.Color.Black
        Me.RadTreeView1.Size = New System.Drawing.Size(150, 250)
        Me.RadTreeView1.SpacingBetweenNodes = -1
        Me.RadTreeView1.TabIndex = 3
        Me.RadTreeView1.Text = "RadTreeView1"
        '
        'CheckBox1
        '
        Me.CheckBox1.AutoSize = True
        Me.CheckBox1.Location = New System.Drawing.Point(168, 23)
        Me.CheckBox1.Name = "CheckBox1"
        Me.CheckBox1.Size = New System.Drawing.Size(81, 17)
        Me.CheckBox1.TabIndex = 4
        Me.CheckBox1.Text = "CheckBox1"
        Me.CheckBox1.UseVisualStyleBackColor = True
        '
        'Form2
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Controls.Add(Me.CheckBox1)
        Me.Controls.Add(Me.RadTreeView1)
        Me.Name = "Form2"
        Me.Text = "Form2"
        CType(Me.RadTreeView1, System.ComponentModel.ISupportInitialize).EndInit()
        Me.ResumeLayout(False)
        Me.PerformLayout()

    End Sub
    Friend WithEvents RadTreeView1 As Telerik.WinControls.UI.RadTreeView


    Private Sub Form2_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        For i = 0 To 20
            Dim node = RadTreeView1.Nodes.Add("node " + i.ToString)
            For j = 0 To 20
                Dim n2 = node.Nodes.Add("node " + i.ToString + " " + j.ToString)
            Next
        Next
        RadTreeView1.LazyMode = True
    End Sub


    Private Sub RadTreeView1_NodeExpandedChanged(sender As System.Object, e As Telerik.WinControls.UI.RadTreeViewEventArgs) Handles RadTreeView1.NodeExpandedChanged
        Dim n = RadTreeView1.SelectedNode
        If n Is Nothing Then Return
        If CheckBox1.Checked Then
            n.Nodes.Clear()
        Else
            While n.Nodes.Count > 0
                n.Nodes.RemoveAt(0)
            End While
        End If
        For i = 0 To 10
            Dim node = n.Nodes.Add("Expando " + i.ToString)
        Next
    End Sub
End Class

My experience with .Net is 7 years. My experience with Rad is about 2 weeks.

• OS version and applied service packs

Microsoft Windows Server 2003, Standard Edition, Service Pack 2

• Regional and language settings, if different from En-US

English (Australia)

• .NET version (.NET2, .NET3, .NET3.5)

.NET 4.0.30319 SP1Rel, Visual Studio 2010 Version 10.0.40219.1 SP1Rel

• Exact version of the Telerik product 

Runtime Version v2.0.50727, Version 2011.2.11.831

[Svett]

Hi Clive,

The best way is to use the NodeExpandedChanging event in this way:

    Private Sub RadTreeView1_NodeExpandedChanging(sender As System.Object, e As Telerik.WinControls.UI.RadTreeViewCancelEventArgs) Handles RadTreeView1.NodeExpandedChanging

        Dim selectedNode = RadTreeView1.SelectedNode

        If selectedNode Is Nothing Then Return

        Me.RadTreeView1.TreeViewElement.BeginUpdate()

        If CheckBox1.Checked Then
            selectedNode.Nodes.Clear()
        Else
            While selectedNode.Nodes.Count > 0
                selectedNode.Nodes.RemoveAt(0)
            End While
        End If

        For i = 0 To 10
            Dim node = selectedNode.Nodes.Add("Expando " + i.ToString)
        Next

        Me.RadTreeView1.TreeViewElement.EndUpdate(False, Telerik.WinControls.UI.RadTreeViewElement.UpdateActions.ItemRemoved)
    End Sub
End Class

I hope this helps. 

Regards,
Svett
the Telerik team

[Adam]

Hi,

Is there a public issue tracked on this?  Or Nodes.Clear() expected to always select the first node in the tree?  I'd like to vote on it if it there is an issue.

-Adam

[Svett]

Hi Adam,

You can vote for the feature request here.

Regards,
Svett
the Telerik team

[Alex]

I have a similar problem. Every call of Node.Clear() scrolls TreeView to first node. This is thery annoying. Telerik version is 2011.3.11.1219. How can I at least remember and restore first visible node, before (I hope) you fix this?

[Svett]

Hello Alex,

You can save the scroll position and get it back after nodes are cleared. You can use the following code snippet as a sample:

int scrollValue = this.radTreeView1.VScrollBar.Value;
int maximum = this.radTreeView1.VScrollBar.Maximum;

this.radTreeView1.Nodes[0].Nodes[0].Nodes[9].Nodes.Clear();

this.radTreeView1.VScrollBar.Value = scrollValue - (int)Math.Abs(this.radTreeView1.VScrollBar.Maximum - maximum);

Greetings,
Svett
the Telerik team