TreeView Check/UnCheck all child items

using your code that you have in the Form_Load keep that code it works and add these 2 methods in your code

private void Form1_Load(object sender, EventArgs e) { treeView1.CheckBoxes = true; treeView1.BeginUpdate(); treeView1.Nodes.Add("1111"); treeView1.Nodes[0].Nodes.Add("2222"); treeView1.Nodes[0].Nodes.Add("2222"); treeView1.Nodes[0].Nodes.Add("2222"); treeView1.Nodes[0].Nodes.Add("2222"); treeView1.Nodes[0].Nodes[1].Nodes.Add("3333"); treeView1.Nodes[0].Nodes[1].Nodes[0].Nodes.Add("4444"); treeView1.Nodes[0].Nodes[1].Nodes[0].Nodes.Add("4444"); treeView1.Nodes[0].Nodes[1].Nodes[0].Nodes.Add("4444"); treeView1.EndUpdate(); treeView1.ExpandAll(); } private void treeView1_AfterCheck(object sender, TreeViewEventArgs e) { foreach (TreeNode childNode in e.Node.Nodes) { childNode.Checked = e.Node.Checked; } } 

The solution that I've figured out was the following:

• To perform the selection I used Linq:

  if (e.Node.Nodes.Count > 0) e.Node.Nodes.Cast<TreeNode>().Where(tnc => tnc.Checked != e.Node.Checked).ForEach(tn => tn.Checked = e.Node.Checked);

• Then to handle the event selection I extended the TreeView class: public class MyTV : TreeView { protected bool TopOfCascade; TreeNode startNode; public Action FinishedCheckEventsDelegate; public Action InitiateCascadeCheckEventsDelegate; public MyTV() : base() { TopOfCascade = false; startNode = null; } protected override void OnBeforeCheck(TreeViewCancelEventArgs e) { base.OnBeforeCheck(e); if (!TopOfCascade && !e.Cancel) { TopOfCascade = true; startNode = e.Node; if (InitiateCascadeCheckEventsDelegate != null) InitiateCascadeCheckEventsDelegate(); } } protected override void OnAfterCheck(TreeViewEventArgs e) { base.OnAfterCheck(e); if (startNode == e.Node && e.Action != TreeViewAction.Unknown) { if (FinishedCheckEventsDelegate != null) FinishedCheckEventsDelegate(); TopOfCascade = false; startNode = null; } } In the host control, you can hook the pre and post cascade events and iterate over all checked/unchecked tree nodes avoiding a lot of cross event firing. You control the cascade via some container.

I got the ForEach to IEnumerable from the following an implementation from the web:

public static void ForEach<T>(this IEnumerable<T> source, Action<T> action) { if (source == null) throw new ArgumentNullException("source"); if (action == null) throw new ArgumentNullException("action"); foreach (T item in source) { action(item); } } 

Good Luck!

Here is an answer (from Hans Passant):

Winforms treeview, recursively check child nodes problem

Im writing it as answer, not comment to make it easier to find.

 private void treeView1_AfterCheck(object sender, TreeViewEventArgs e) { if (e.Action != TreeViewAction.Unknown) { if (e.Node.Nodes.Count > 0) { /* Calls the CheckAllChildNodes method, passing in the current Checked value of the TreeNode whose checked state changed. */ this.CheckAllChildNodes(e.Node, e.Node.Checked); } } } private void CheckAllChildNodes(TreeNode treeNode, bool nodeChecked) { foreach (TreeNode node in treeNode.Nodes) { node.Checked = nodeChecked; if (node.Nodes.Count > 0) { // If the current node has child nodes, call the CheckAllChildsNodes method recursively. this.CheckAllChildNodes(node, nodeChecked); } } } 

 private void CheckAllChildNodes(TreeNode treeNode, bool nodeChecked) { foreach (TreeNode node in treeNode.Nodes) { node.Checked = nodeChecked; if (node.Nodes.Count > 0) { this.CheckAllChildNodes(node, nodeChecked); } } } private void treeView_AfterCheck(object sender, TreeViewEventArgs e) { if (e.Action != TreeViewAction.Unknown) { if (e.Node.Nodes.Count > 0) { if (!e.Node.Checked) { this.CheckAllChildNodes(e.Node, e.Node.Checked); } } } if (e.Node.Parent != null) { TreeNode n = e.Node; while (n.Parent != null) { if (n.Checked) { n.Parent.Checked = true; } n = n.Parent; } } }