TreeNodeEnumerator Class

public class TreeNodeEnumerator : IEnumerator

txtEnumResults.Text = null;

// Use foreach() on the ExtendedTreeView control itself to
// enumerate all of its nodes recursively.
foreach(TreeNode node in tvExtTree)
    txtEnumResults.AppendText($"{new String(' ', node.Level * 4)}{node.Text}\r\n");

Dim node As TreeNode
txtEnumResults.Text = Nothing

' Use For Each on the ExtendedTreeView control itself to enumerate all of its nodes recursively
For Each node in tvExtTree
    txtEnumResults.AppendText($"{New String(" "C, node.Level * 4)}{node.Text}" & Environment.NewLine)
Next

bool enumerateSiblings = (sender == btnEnumNodeSibs);
TreeNode node, startNode = tvExtTree.SelectedNode;

if(startNode == null)
{
    txtEnumResults.Text = "Select a starting node first";
    return;
}

txtEnumResults.Text = null;

// For this, we create the enumerator manually and pass it
// the starting node and a flag indicating whether or not
// to enumerate the siblings of the starting node as well.
TreeNodeEnumerator enumerator = new(startNode, enumerateSiblings);

// Call the MoveNext() method to move through each node.  Use the
// Current property to access the current node.
while(enumerator.MoveNext())
{
    node = enumerator.Current!;

    txtEnumResults.AppendText($"Manual Enum: {new String(' ', node.Level * 4)}{node.Text}\r\n");
}

txtEnumResults.AppendText("\r\n\r\n");

// We can also use the helper method to simplify it
foreach(TreeNode tn in TreeNodeEnumerator.Enumerate(startNode, enumerateSiblings))
    txtEnumResults.AppendText($"Enum Helper: {new String(' ', tn.Level * 4)}{tn.Text}\r\n");

Dim enumerateSiblings As Boolean = False
Dim node As TreeNode
Dim startNode As TreeNode = tvExtTree.SelectedNode

If sender Is btnEnumNodeSibs Then
    enumerateSiblings = True
End If

If startNode Is Nothing Then
    txtEnumResults.Text = "Select a starting node first"
    Return
End If

txtEnumResults.Text = Nothing

' For this, we create the enumerator manually and pass it the starting
' node and a flag indicating whether or not to enumerate the siblings
' of the starting node as well.
Dim enumerator As New TreeNodeEnumerator(startNode, enumerateSiblings)

' Call the MoveNext() method to move through each node.  Use the Current
' property to access the current node.
Do While enumerator.MoveNext()
    node = enumerator.Current

    txtEnumResults.AppendText($"Manual Enum: {New String(" "C, node.Level * 4)}{node.Text}" &
        Environment.NewLine)
Loop

txtEnumResults.AppendText(Environment.NewLine & Environment.NewLine)

' We can also use the helper method to simplify it
For Each node In TreeNodeEnumerator.Enumerate(startNode, enumerateSiblings)
    txtEnumResults.AppendText($"Enum Helper: {New String(" "C, node.Level * 4)}{node.Text}" &
        Environment.NewLine)
Next