c# - What algorithm is used in this code? -

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this code checks , unchecks child nodes of treeview control. algorithm used in code?

private int _callcountup;  private int _callcountdn;  private void tvwpermissions_aftercheck(object sender, system.windows.forms.treevieweventargs e)         {             bool anychecked = false;              if (_callcountdn == 0 && e.node.parent != null)             {                 anychecked = false;                 foreach (treenode childnode in e.node.parent.nodes)                 {                     if (childnode.checked)                     {                         anychecked = true;                         break;                     }                 }                 _callcountup += 1;                  if (anychecked)                     e.node.parent.checked = true;                  _callcountup -= 1;             }              if (_callcountup == 0)             {                 foreach (treenode childnode in e.node.nodes)                 {                     _callcountdn += 1;                     childnode.checked = e.node.checked;                     _callcountdn -= 1;                 }             }         }

not sure has name. quite standard, _callcountup/dn fields avoid trouble when changing checked property of node causes aftercheck event handler run again. stackoverflow typical outcome when event handler recurses without bound.

the generic pattern resembles this:

private bool modifyingnodes;  private void treeview_aftercheck(object sender, treevieweventargs e) {     if (modifyingnodes) return;     modifyingnodes = true;     try {        // etc..     }     {        modifyingnodes = false;     } }

the block ensures handled exception (such through threadexceptiondialog) doesn't permanently leave state variable set true. it's optional of course.


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