Question

Tree View control’s AfterCheck event checks all child nodes below it and enables the Run button if something is checked.

1346 void TreeNode_AfterCheck(object sender, TreeViewEventArgs e) {
1347   if (!e.Node.Checked) return;
1348   foreach (TreeNode sub in e.Node.Nodes) {
1349     sub.Checked = e.Node.Checked;
1350   }
1351   RunButton.Enabled = IsANodeChecked();
1352 }

1429 static bool IsANodeChecked(TreeNode node) {
1430   if (node.Checked) return true;
1431   foreach (TreeNode sub in node.Nodes) {
1432     if (IsANodeChecked(sub)) {
1433       return true;
1434     }
1435   }
1436   return false;
1437 }

Checking the root node when there are 4881 sub nodes will hang the GUI for about 7 seconds.

I only need to call IsANodeChecked (on Line 1351) once, but I don’t know how to disable it until after all of the tree nodes have been processed.

And I do not want to have a timer on my form devoted to monitoring this.

Does anyone see a simple/obvious solution?

Answer 1

These ideas where helpful, but I used something different that worked by adding a single boolean variable:

bool _treeNodeFirst = false;

…and a Before Checked event that temporarily modifies the Back Color on the control to serve as a flag for the control that started the chain of events:

1273 void TreeNode_BeforeCheck(object sender, TreeViewCancelEventArgs e) {
1274   if (!_treeNodeFirst) {
1275     _treeNodeFirst = true;
1276     e.Node.BackColor = Color.Silver;
1277   }
1278 }

1346 void TreeNode_AfterCheck(object sender, TreeViewEventArgs e) {
1347   if (e.Node.Checked) {
1348     foreach (TreeNode sub in e.Node.Nodes) {
1349       sub.Checked = e.Node.Checked;
1350     }
1351   }
1352   if (e.Node.BackColor == Color.Silver) {
1353     e.Node.BackColor = Color.Empty;
1354     RunButton.Enabled = IsANodeChecked();
1355     _treeNodeFirst = false;
1356   }
1357 }

1429 static bool IsANodeChecked(TreeNode node) {
1430   if (node.Checked) return true;
1431   foreach (TreeNode sub in node.Nodes) {
1432     if (IsANodeChecked(sub)) {
1433       return true;
1434     }
1435   }
1436   return false;
1437 }

This seems to be the best way (that I can see right now) to ensure that IsANodeChecked(TreeNode) is only run once when a group of nodes is selected all at once.

I do, however, really like Jimmy Hoffa’s idea of using a count, though. I will probably add that to my code.

Thanks to all!
~Joe