Question

I have a Tree View control for a Windows Application that uses the CheckBoxes property.

Sometimes (often) when a Tree Node is either checked or unchecked, I get Stack Overflow Exceptions in my static methods below.

Could someone point out why? Maybe even show me how to do this the right way?

In the After Check Event, I have written the following:

void TreeNode_AfterCheck(object sender, TreeViewEventArgs e) {
  if (0 < e.Node.Nodes.Count) {
    if (e.Node.Checked) {
      e.Node.Expand();
      TreeNodes_SetChecksTo(e.Node, true);
    } else {
      if (!TreeNode_SomethingChecked(e.Node)) {
        e.Node.Collapse(false);
      }
    }
  }
}

Generally, the Exception is thrown when something in a static method fires the After Check Event above and trickles into one of the static methods below:

static void TreeNodes_SetChecksTo(TreeNode node, bool value) {
  if (node != null) {
    if (node.Checked != value) node.Checked = value;
    if (0 < node.Nodes.Count) {
      foreach (TreeNode sub in node.Nodes) {
        TreeNodes_SetChecksTo(sub, value);
      }
    }
  }
}

static bool TreeNode_SomethingChecked(TreeNode node) {
  if (node != null) {
    if (node.Checked) return true;
    if (0 < node.Nodes.Count) {
      foreach (TreeNode sub in node.Nodes) {
        if (TreeNode_SomethingChecked(sub)) {
          return true;
        }
      }
    }
  }
  return false;
}

Answer 1

Setting IsChecked inside TreeNodes_SetChecksTo is resulting in the AfterCheck event being raised and thus the TreeNode_AfterCheck method being called. I suspect you want to disable/ignore the event whilst processing it:

private bool latch;

void TreeNode_AfterCheck(object sender, TreeViewEventArgs e) {
  if (latch)
      return;

  latch = true;

  try
  {
      if (0 < e.Node.Nodes.Count) {
        if (e.Node.Checked) {
          e.Node.Expand();
          TreeNodes_SetChecksTo(e.Node, true);
        } else {
          if (!TreeNode_SomethingChecked(e.Node)) {
            e.Node.Collapse(false);
          }
        }
      }
  }
  finally
  {
      latch = false;
  }
}