To reproduce:
- Add a lot of nodes to the tree (scrollbars must appear).
- Use the following code to add nodes:
public RadForm1()
{
    InitializeComponent();
    radTreeView1.AllowEdit = true;
    RadContextMenu menu = new RadContextMenu();
    RadMenuItem add = new RadMenuItem();
    add.Click += add_Click;
    add.Text = "add";
    menu.Items.Add(add);
    radTreeView1.RadContextMenu = menu;

}
void add_Click(object sender, EventArgs e)
{
    RadTreeNode node = radTreeView1.SelectedNode;

    var newNode = node.Nodes.Add("new node");
    node.Expanded = true;
    radTreeView1.SelectedNode = newNode;
    radTreeView1.BeginEdit();
}
- Add a node and scroll

Workaround:
public RadForm1()
{
    InitializeComponent();
    radTreeView1.TreeViewElement.VScrollBar.Scroll += VScrollBar_Scroll;
    radTreeView1.MouseWheel += TreeViewElement_MouseWheel;
}

void TreeViewElement_MouseWheel(object sender, MouseEventArgs e)
{
    var radTreeView = sender as RadTreeView;
    if (radTreeView.IsEditing)
    {
        radTreeView.EndEdit();
    }
}

void VScrollBar_Scroll(object sender, ScrollEventArgs e)
{
    var radTreeView = (sender as RadScrollBarElement).ElementTree.Control as RadTreeView;
    if (radTreeView.IsEditing)
    {
        radTreeView.EndEdit();
    }
}

To reproduce:
- Add items to the tree view (scrollbar must appear)
- Add context menu item which adds a new node and puts it in edit mode.
- Add a new node with the context menu item, scroll to the bottom, add item again.
- Scroll up and add item one more time.

Workaround:
void treeView_EditorRequired(object sender, TreeNodeEditorRequiredEventArgs e)
{
    e.Editor = new TreeViewTextBoxEditor();
}

To reproduce: 
           radTreeView1.CheckBoxes = true;
            radTreeView1.TriStateMode = true;
            radTreeView1.AutoCheckChildNodes = true;

            RadTreeNode root = radTreeView1.Nodes.Add("Home");
            root.Expanded = true;

            RadTreeNode node1 = new RadTreeNode("Minimal");
            node1.CheckState = Telerik.WinControls.Enumerations.ToggleState.On;

            root.Nodes.Add(node1);

Workaround: first add the node to the Nodes collection and only then set its CheckState

Workaround:

After updating the binding source reset the data source of the tree

this.radTreeView.DataSource = null;

this.radTreeView.DataSource = this.MyBindingSource;

Workaround:  add RadTreeNodes at run time.

To reproduce:

public Form1()
{
    InitializeComponent();

    for (int i = 0; i < 20; i++)
    {
        this.radTreeView1.Nodes.Add("Node"+i);
    }
    this.radTreeView1.AllowEdit = true;
}

The attached gif file illustrates the steps.

Workaround:
 this.radTreeView1.VScrollBar.ValueChanged+=VScrollBar_ValueChanged;
private void VScrollBar_ValueChanged(object sender, EventArgs e)
{
    this.radTreeView1.EndEdit();
}

To reproduce:

public Form1()
{
    InitializeComponent();

    this.radTreeView1.AllowDragDrop = true;
    this.radTreeView2.AllowDragDrop = true;
    for (int i = 0; i < 5; i++)
    {
        this.radTreeView1.Nodes.Add("Node1." + i);
        this.radTreeView2.Nodes.Add("Node2." + i);
    }
    this.radTreeView1.ScreenTipNeeded += radTreeView1_ScreenTipNeeded;
    this.radTreeView2.ScreenTipNeeded += radTreeView1_ScreenTipNeeded;
}

RadOffice2007ScreenTipElement _screenTip = new RadOffice2007ScreenTipElement();

private void radTreeView1_ScreenTipNeeded(object sender, Telerik.WinControls.ScreenTipNeededEventArgs e)
{
    _screenTip.CaptionLabel.Text = "Caption";
    _screenTip.MainTextLabel.Text = "text";
    _screenTip.AutoSize = true;
    e.Delay = 2000;
    e.Item.ScreenTip = _screenTip;
}

Steps:
1. Drag a node from the first RadTreeView to the other while the screen-tip is shown for the dragged node.
2. When the screen-tip is about to be hidden, the error occurs.

Workaround:

private void radTreeView1_DragStarting(object sender, RadTreeViewDragCancelEventArgs e)
{
    if (_screenTip.IsElementVisible)
    {
        this.radTreeView1.Behavior.HideScreenTip();
    }
   
}

To reproduce: use the following code:

public Form1()
{
    InitializeComponent();

    this.radTreeView1.MultiSelect = true;
    for (int i = 0; i < 3; i++)
    {
        RadTreeNode node = new RadTreeNode();
        node.Text = "Node." + i;
        for (int j = 0; j < 3; j++)
        {
            node.Nodes.Add(new RadTreeNode("Node." + i + "." + j));
        }
        this.radTreeView1.Nodes.Add(node);
    }
    this.radTreeView1.SelectedNodeChanged += radTreeView1_SelectedNodeChanged;
}

private void radTreeView1_SelectedNodeChanged(object sender, Telerik.WinControls.UI.RadTreeViewEventArgs e)
{
    Console.WriteLine(e.Node.Text + ">> Selected: " + e.Node.Selected);
}

1.Select a node
2.Press Ctrl and click over the selected node again in order to unselect it. The SelectedNodeChanged event will not fire.

Workaround:

public class MyRadTreeNode : RadTreeNode
{
    public MyRadTreeNode(string text) : base(text)
    {
    }
    
    private static readonly MethodInfo OnSelectedNodeChangedMethodInfo =
        typeof(RadTreeViewElement).GetMethod("OnSelectedNodeChanged",
            BindingFlags.NonPublic | BindingFlags.Instance, null,
            new Type[] { typeof(RadTreeNode), typeof(RadTreeViewAction) }, null);

    protected override void OnNotifyPropertyChanged(PropertyChangedEventArgs args)
    {
        base.OnNotifyPropertyChanged(args);

        if (args.PropertyName == "Selected" && TreeViewElement != null)
        {
            OnSelectedNodeChangedMethodInfo.Invoke(TreeViewElement, new object[] { this, RadTreeViewAction.ByMouse });
        }
    }
}

Error: "Object of type 'Telerik.WinControls.Enumerations.ToggleState' cannot be converted to type 'System.Boolean'."

To reproduce:

public Form1()
{
    InitializeComponent();

    List<Parent> dataItems = new List<Parent>();
    Parent currentParent;
    Child currentChild;
    List<Child> children;
    string parentId = string.Empty;
    string childId = string.Empty;
    for (int i = 1; i <= 5; i++)
    {
        parentId = Guid.NewGuid().ToString();

        children = new List<Child>();
        for (int j = 1; j < 5; j++)
        {
            childId = Guid.NewGuid().ToString();
            currentChild = new Child(childId, parentId, "SubNode." + i + "." + j, j % 2 == 0);
            children.Add(currentChild);
        }
        currentParent = new Parent(parentId, "Node." + i, i % 2 == 0,children);
        dataItems.Add(currentParent);
    }

    radTreeView1.DataSource = dataItems;
    radTreeView1.DisplayMember = "Title\\Name";
    radTreeView1.ChildMember = "Parent\\Children";
    radTreeView1.CheckedMember = "IsActive\\Status";
    radTreeView1.CheckBoxes = true;
}

public class Parent 
{
    public string ParentId { get; set; }

    public string Title { get; set; }

    public bool IsActive { get; set; }

    public List<Child> Children { get; set; }

    public Parent(string parentId, string title, bool isActive, List<Child> children)
    {
        this.ParentId = parentId;
        this.Title = title;
        this.IsActive = isActive;
        this.Children = children;
    }
}

public class Child
{
    public string ChildId { get; set; }

    public string ParentId { get; set; }

    public string Name { get; set; }

    public bool Status { get; set; }

    public Child(string childId, string parentId, string name, bool status)
    {
        this.ChildId = childId;
        this.ParentId = parentId;
        this.Name = name;
        this.Status = status;
    }
}

Workaround: Use a custom TypeConverter for the boolean properties:

public class ToggleStateConverter : TypeConverter
{
    public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
    {
        return destinationType == typeof(ToggleState);
    }

    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
    {
        if (value is bool)
        {
            switch ((bool)value)
            {
                case true:
                    return ToggleState.On;
                case false:
                    return ToggleState.Off;
                default :
                    return ToggleState.Indeterminate;
            }
        }
        return base.ConvertTo(context, culture, value, destinationType);
    }

    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
        return sourceType == typeof(ToggleState);
    }

    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        ToggleState state = (ToggleState)value;

        switch (state)
        {
            case ToggleState.On:
                return true;
            case ToggleState.Off:
                return false;
            case ToggleState.Indeterminate:
                return false;
        }

        return base.ConvertFrom(context, culture, value);
    }
}

To reproduce: use the following code snippet and perform the illustrated steps on the attached gif file:

public Form1()
{
    InitializeComponent();

    for (int i = 0; i < 5; i++)
    {
        this.radTreeView1.Nodes.Add("Node" + i);
    }

    this.radTreeView1.NodeRemoving += radTreeView1_NodeRemoving;

    this.radTreeView1.AllowRemove = true;
    this.radTreeView1.AllowDefaultContextMenu = true;
}

private void radTreeView1_NodeRemoving(object sender, Telerik.WinControls.UI.RadTreeViewCancelEventArgs e)
{
    DialogResult result = RadMessageBox.Show(String.Format("Do you really want to remove the node '{0}'?", e.Node.Text),
        "Question", System.Windows.Forms.MessageBoxButtons.YesNo, RadMessageIcon.Question);

    if (result != System.Windows.Forms.DialogResult.Yes)
    {
        e.Cancel = true;
    }
}

Please refer to the attached gif file.

Workaround: set the Enabled property to false at run time.

Workaround:

class CustomDragDropService : TreeViewDragDropService
{
    public CustomDragDropService(RadTreeViewElement owner) : base(owner)
    {
        
    }

    protected override void SetHintWindowPosition(Point mousePt)
    {
    }
}

class CustomTreeViewElement : RadTreeViewElement
{
    protected override Type ThemeEffectiveType
    {
        get
        {
            return typeof(RadTreeViewElement);
        }
    }

    protected override TreeViewDragDropService CreateDragDropService()
    {
        return new CustomDragDropService(this);
    }
}

class CustomTreeView : RadTreeView
{
    protected override RadTreeViewElement CreateTreeViewElement()
    {
        return new CustomTreeViewElement();
    }

    public override string ThemeClassName
    {
        get
        {
            return typeof(RadTreeView).FullName;
        }
    }
}

To reproduce: 
1. Run Demo application >> TreeView >> Drag & Drop.
2. Change the theme to Windows7 and start dragging a node.

The drop hint is missing.

Workaround: apply the theme in the Form.Load event after getting the TreeViewElement.ItemDropHint property coming from the ControlDefault theme.

RadImageShape hint;

private void Form1_Load(object sender, EventArgs e)
{
    hint = this.radTreeView1.TreeViewElement.ItemDropHint;
    this.radTreeView1.ThemeName = "Windows7";
    this.radTreeView1.TreeViewElement.ItemDropHint = hint;
}

To reproduce: add a RadTreeView and a RadButton to the form. Use the following code snippet:

public Form1()
{
    InitializeComponent();

    RadTreeNode node1 = new RadTreeNode();
    node1.Text = "SameText";

    RadTreeNode node2 = new RadTreeNode();
    node2.Text = "SameText";

    this.radTreeView1.Nodes.Add(node1);
    this.radTreeView1.Nodes.Add(node2);

    this.radTreeView1.SortOrder = SortOrder.Ascending;
}

private void radButton1_Click(object sender, EventArgs e)
{
    for (int i = this.radTreeView1.Nodes.Count - 1; i > -1; i--)
    {
        this.radTreeView1.Nodes.RemoveAt(i);
    }
}

Workaround: set the SortOrder property to None before removing the nodes and restore it afterwards

private void radButton1_Click(object sender, EventArgs e)
{
    this.radTreeView1.SortOrder = SortOrder.None;
    for (int i = this.radTreeView1.Nodes.Count - 1; i > -1; i--)
    {
        this.radTreeView1.Nodes.RemoveAt(i);
    }
    this.radTreeView1.SortOrder = SortOrder.None;
}

If you set the RadBreadCrumb.DefaultTreeView property to null, all items in the RadBreadCrumb should be cleared. Additionally, the subscription to the SelectedNodeChanged remains although the associated tree view is set to null. Afterwards, if you change the selected node, a NullReferenceException occurs.

To reproduce: 
1. Add a RadTreeView and populate it with nodes at design time.
2. Use the following code snippet:

Me.RadTreeView1.AllowDefaultContextMenu = True
Me.RadTreeView1.RightToLeft = Windows.Forms.RightToLeft.Yes

When you run the application and right click over a node, the context menu is not in RTL mode.

Workaround: use the ContextMenuOpening event and set the TreeViewDefaultContextMenu.RightToLeft property to Yes.

Private Sub RadTreeView1_ContextMenuOpening(sender As Object, e As TreeViewContextMenuOpeningEventArgs) _
    Handles RadTreeView1.ContextMenuOpening
    Dim defaultMenu As TreeViewDefaultContextMenu = TryCast(e.Menu, TreeViewDefaultContextMenu)
    If defaultMenu IsNot Nothing Then
        defaultMenu.DropDown.RightToLeft = Windows.Forms.RightToLeft.Yes
    End If
End Sub

Workaround: use the NodeFormatting event to set the NodeElement.ExpanderElement.Padding to new Padding(1, 0, 0, 0)

Workaround:

 class MyTreeView : RadTreeView
        {
            protected override RadTreeViewElement CreateTreeViewElement()
            {
                return new MyTreeViewElement();
            }

            public override string ThemeClassName
            {
                get
                {
                    return typeof(RadTreeView).FullName;
                }
            }
        }

        class MyTreeViewElement : RadTreeViewElement
        {
            bool IsPerformingEndEdit = false;
            protected override bool EndEditCore(bool commitChanges)
            {
                if (!IsEditing || IsPerformingEndEdit)
                {
                    return false;
                }

                TreeNodeElement nodeElement = GetElement(this.SelectedNode);
                if (nodeElement == null)
                {
                    return false;
                }

                this.IsPerformingEndEdit = true;

                if (commitChanges && this.ActiveEditor.IsModified)
                {
                    SaveEditorValue(nodeElement, this.ActiveEditor.Value);
                }

                this.ActiveEditor.EndEdit();
                nodeElement.RemoveEditor(this.ActiveEditor);

                this.InvalidateMeasure();
                UpdateLayout();

                OnEdited(new TreeNodeEditedEventArgs(nodeElement, ActiveEditor, !commitChanges));

                typeof(RadTreeViewElement).GetField("activeEditor", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).SetValue(this, null); 

                this.IsPerformingEndEdit = false;

                return false;
            }

            protected override Type ThemeEffectiveType
            {
                get
                {
                    return typeof(RadTreeViewElement);
                }
            }
        }