Start dragging a node and scroll using the mouse wheel. While scrolling, drop the node. 

To reproduce: 


protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);


    radTreeView1 = new RadTreeView();
    radTreeView1.Parent = this;


    for (int i = 0; i < 5; i++)
    {
        RadTreeNode n1 = new RadTreeNode("Node" + i);
        this.radTreeView1.Nodes.Add(n1);
        if (i % 2 == 0)
        {
            for (int j = 0; j < 2; j++)
            {
                RadTreeNode n2 = new RadTreeNode("Node" + i + "." + j);
                n1.Nodes.Add(n2);


                if (j % 2 == 0)
                {
                    for (int k = 0; k < 2; k++)
                    {
                        RadTreeNode n3 = new RadTreeNode("Node" + i + "." + j + "." + k);
                        n2.Nodes.Add(n3);
                    }
                }
            }
        }
    }
    radTreeView1.ShowRootLines = false;
    radTreeView1.ShowLines = false;
}


Workaround:

void radTreeView1_NodeFormatting(object sender, TreeNodeFormattingEventArgs e)
{
    if (radTreeView1.ShowLines == false)
    {
        if (e.NodeElement.LinesContainerElement.Children.Count > 0)
        {
            TreeNodeLineElement lineElement = (TreeNodeLineElement)e.NodeElement.LinesContainerElement.Children[0];
            lineElement.Visibility = ElementVisibility.Collapsed;
        }
    }
}

To reproduce
- Add RadTreeView with some nodes to a blank form.
- Set the MultiSelect property to true.
- Select\Deselect a node with code.
 
Resolution: 
The SelectedNodeChanged event should not be fired when selected/deselected the node programmatically. We added a new event SelectedNodesChanged which is fired when the SelectedNodes collection changes.

To reproduce:
- Add treeview to a form and set its AutoScrollOnClick property to false.
- click a node that is not entirely visible with the right mouse button.
- You will notice that the view is auto scrolled.

To reproduce:
- Add RadTreeView to a blank form.
- Set its AllowDragDrop and AllowDefaultContextMenu properties to true.
- Clear the menu items in the  ContextMenuOpening event.
- You will notice that the Copy, Cut and Paste items are not removed.

Workaround:
 void radTreeView1_ContextMenuOpening(object sender, Telerik.WinControls.UI.TreeViewContextMenuOpeningEventArgs e)
{
   
    e.Menu.DropDownOpened -= Menu_DropDownOpened; 
    e.Menu.DropDownOpened += Menu_DropDownOpened; 
}

void Menu_DropDownOpened(object sender, EventArgs e)
{
    TreeViewDefaultContextMenu Menu = sender as TreeViewDefaultContextMenu;

    for (int i = Menu.Items.Count - 1; i >= 0; i--)
    {
        if (Menu.Items[i].Name == "Copy" || Menu.Items[i].Name == "Cut" || Menu.Items[i].Name == "Paste")
        {
            Menu.Items.Remove(Menu.Items[i]);
        }
    }
}

To reproduce: use the following code

public class Item
{
    public int Id { get; set; }

    public string Title { get; set; }

    public string Tag { get; set; }

    public Item(int id, string title, string tag)
    {
        this.Id = id;
        this.Title = title;
        this.Tag = tag;
    }
}

public Form1()
{
    InitializeComponent();

    List<Item> items = new List<Item>();
    items.Add(new Item(1,"a1","x1"));
    items.Add(new Item(2,"a2","x2"));
    items.Add(new Item(3,"a3","x3"));
    items.Add(new Item(4,"b1","y1"));
    items.Add(new Item(5,"b2","y2"));
    items.Add(new Item(6,"b3","y3"));
    this.radTreeView1.DataSource = items;
    this.radTreeView1.DisplayMember = "Title";
    this.radTreeView1.ValueMember = "Id";
   
    radTreeView1.FilterDescriptors.Add(new FilterDescriptor("Tag", FilterOperator.Contains, "y"));
}

Workaround: use custom filtering:
public Form1()
{
    InitializeComponent();

    List<Item> items = new List<Item>();
    items.Add(new Item(1,"a1","x1"));
    items.Add(new Item(2,"a2","x2"));
    items.Add(new Item(3,"a3","x3"));
    items.Add(new Item(4,"b1","y1"));
    items.Add(new Item(5,"b2","y2"));
    items.Add(new Item(6,"b3","y3"));
    this.radTreeView1.DataSource = items;
    this.radTreeView1.DisplayMember = "Title";
    this.radTreeView1.ValueMember = "Id";
   
    radTreeView1.FilterDescriptors.Add(new FilterDescriptor("Tag", FilterOperator.Contains, "y")); 
    radTreeView1.TreeViewElement.FilterPredicate = FilterNode;
}

public class Item
{
    public int Id { get; set; }

    public string Title { get; set; }

    public string Tag { get; set; }

    public Item(int id, string title, string tag)
    {
        this.Id = id;
        this.Title = title;
        this.Tag = tag;
    }
}

private bool FilterNode(RadTreeNode node)
{
    Item item = node.DataBoundItem as Item;
  
    if (item != null && radTreeView1.FilterDescriptors.Count > 0)
    { 
        FilterDescriptor fd = radTreeView1.FilterDescriptors[0];
        var propertyValue = item.GetType().GetProperty(fd.PropertyName,
            BindingFlags.Public | BindingFlags.Instance).GetValue(item, null);
        if (propertyValue.ToString().Contains(fd.Value.ToString()))
        {
            return true;
        }
        return false;
    }

    return false;
}

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);
                }
            }
        }

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;
}

Please refer to the attached gif file.

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

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;
    }
}

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:

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 });
        }
    }
}

Workaround:  add RadTreeNodes at run time.

Workaround:

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

this.radTreeView.DataSource = null;

this.radTreeView.DataSource = this.MyBindingSource;

Workaround:

this.radTreeView1.EnableRadAccessibilityObjects = false;

To reproduce:

private void Form1_Load(object sender, EventArgs e)
{ 
    this.radTreeView1.Nodes.Add("Node1");
    this.radTreeView1.Nodes.Add("Node2");
    this.radTreeView1.Nodes.Add("Node3");
    this.radTreeView1.Nodes.Add("Node4");
    this.radTreeView1.Nodes.Add("Node5");
    this.radTreeView1.Nodes.Add("Node6");
    this.radTreeView1.Nodes["Node1"].Nodes.Add("Node11");
    this.radTreeView1.Nodes["Node1"].Nodes.Add("Node12");
    this.radTreeView1.Nodes["Node1"].Nodes.Add("Node13");
    this.radTreeView1.Nodes["Node1"].Nodes.Add("Node14");
    this.radTreeView1.Nodes["Node2"].Nodes.Add("Node21");
    this.radTreeView1.Nodes["Node2"].Nodes.Add("Node22");
    this.radTreeView1.Nodes["Node2"].Nodes.Add("Node23");
    this.radTreeView1.Nodes["Node2"].Nodes.Add("Node24");
    this.radTreeView1.Nodes["Node3"].Nodes.Add("Node31");
    this.radTreeView1.Nodes["Node3"].Nodes.Add("Node32");
    this.radTreeView1.Nodes["Node3"].Nodes.Add("Node33");
    this.radTreeView1.Nodes["Node3"].Nodes.Add("Node34");
    this.radTreeView1.Nodes["Node4"].Nodes.Add("Node41");
    this.radTreeView1.Nodes["Node4"].Nodes.Add("Node42");
    this.radTreeView1.Nodes["Node4"].Nodes.Add("Node43");
    this.radTreeView1.Nodes["Node4"].Nodes.Add("Node44");
    this.radTreeView1.Nodes["Node5"].Nodes.Add("Node51");
    this.radTreeView1.Nodes["Node5"].Nodes.Add("Node52");
    this.radTreeView1.Nodes["Node5"].Nodes.Add("Node53");
    this.radTreeView1.Nodes["Node5"].Nodes.Add("Node54");
    this.radTreeView1.Nodes["Node6"].Nodes.Add("Node61");
    this.radTreeView1.Nodes["Node6"].Nodes.Add("Node62");
    this.radTreeView1.Nodes["Node6"].Nodes.Add("Node63");
    this.radTreeView1.Nodes["Node6"].Nodes.Add("Node64");
}

Workaround: add the nodes in the form's constructor.

Second workaround:  Me.RadTreeView1.TreeViewElement.Update(Telerik.WinControls.UI.RadTreeViewElement.UpdateActions.Reset)

Workaround:

raise a flag before the delete operation and cancel the SelectedNodeChanging event

To reproduce:

DataTable dt = new DataTable();
 
public Form1()
{
    InitializeComponent();

    dt.Columns.Add("Id", typeof(int));
    dt.Columns.Add("ParentID", typeof(int));
    dt.Columns.Add("NodeName", typeof(string));
    dt.Rows.Add(1, 0, "Category1");
    dt.Rows.Add(2, 1, "Category2");
    dt.Rows.Add(3, 0, "Category3");
    dt.Rows.Add(4, 3, "Category4");
    dt.Rows.Add(5, 3, "Category5");
    dt.Rows.Add(6, 3, "Category6");
    dt.Rows.Add(7, 6, "Category7");
    dt.Rows.Add(8, 6, "Category8"); 

    this.radTreeView1.DataSource = dt; 

    this.radTreeView1.DisplayMember = "NodeName";
    this.radTreeView1.ChildMember = "ID";
    this.radTreeView1.ParentMember = "ParentID";

    this.radTreeView1.ExpandAll();

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

    this.radLabel1.Text = "Number of rows: " + dt.Rows.Count;
    
    this.radTreeView1.NodeRemoved += radTreeView1_NodeRemoved;
}

private void radTreeView1_NodeRemoved(object sender, Telerik.WinControls.UI.RadTreeViewEventArgs e)
{
    this.radLabel1.Text = "Number of rows: " + dt.Rows.Count;
}

Workaround: perform the delete operation programmatically by modifying the default context menu:

 this.radTreeView1.ContextMenuOpening += radTreeView1_ContextMenuOpening;

private void radTreeView1_ContextMenuOpening(object sender, TreeViewContextMenuOpeningEventArgs e)
{
    foreach (RadMenuItem item in e.Menu.Items)
    {
        if (item.Text == "&Delete")
        {
            item.Visibility = Telerik.WinControls.ElementVisibility.Collapsed;
        }
        else
        {
            item.Visibility = Telerik.WinControls.ElementVisibility.Visible;
        }
    }

    RadMenuItem removeItem = new RadMenuItem("Remove");
    e.Menu.Items.Add(removeItem);
    removeItem.Click += item_Click;
}

private void item_Click(object sender, EventArgs e)
{
    DeleteSubNodes(this.radTreeView1.SelectedNode);
    this.radLabel1.Text = "Number of rows: " + dt.Rows.Count;
}

private void DeleteSubNodes(Telerik.WinControls.UI.RadTreeNode node)
{
    if (node.Nodes.Count == 0)
    {
        dt.Rows.Remove(((DataRowView)node.DataBoundItem).Row);
    }
    else
    {
        foreach (RadTreeNode n in node.Nodes)
        {
            DeleteSubNodes(n);
        }
        dt.Rows.Remove(((DataRowView)node.DataBoundItem).Row);
    }
}

To reproduce:
- Open the Property builder, add some nodes and disable them.
- There is no way to enable them at design time. 

Workaround. 
Disable the nodes at runtime.