// from http://geekswithblogs.net/ranganh/archive/2009/01/21/updated-asp.net-treeview-checkboxes-ndash-check-all-ndash-javascript.aspx
function OnCheckBoxCheckChanged(evt) {
	var src = window.event != window.undefined ? window.event.srcElement : evt.target;
	var isChkBoxClick = (src.tagName.toLowerCase() == "input" && src.type == "checkbox");
	if (isChkBoxClick) {
		var parentTable = GetParentByTagName("table", src);
		var nxtSibling = parentTable.nextSibling;
		if (nxtSibling && nxtSibling.nodeType == 1)//check if nxt sibling is not null & is an element node
		{
			if (nxtSibling.tagName.toLowerCase() == "div") //if node has children
			{
				//check or uncheck children at all levels
				CheckUncheckChildren(parentTable.nextSibling, src.checked);
			}
		}
		//check or uncheck parents at all levels
		CheckUncheckParents(src, src.checked);
	}
}
function CheckUncheckChildren(childContainer, check) {
	var childChkBoxes = childContainer.getElementsByTagName("input");
	var childChkBoxCount = childChkBoxes.length;
	for (var i = 0; i < childChkBoxCount; i++) {
		childChkBoxes[i].checked = check;
	}
}
function CheckUncheckParents(srcChild, check) {
	var parentDiv = GetParentByTagName("div", srcChild);
	var parentNodeTable = parentDiv.previousSibling;

	if (parentNodeTable) {
		var checkUncheckSwitch;

		if (check) //checkbox checked
		{
			var isAllSiblingsChecked = AreAllSiblingsChecked(srcChild);
			if (isAllSiblingsChecked)
				checkUncheckSwitch = true;
			else
				return; //do not need to check parent if any(one or more) child not checked
		}
		else //checkbox unchecked
		{
			checkUncheckSwitch = false;
		}

		var inpElemsInParentTable = parentNodeTable.getElementsByTagName("input");
		if (inpElemsInParentTable.length > 0) {
			var parentNodeChkBox = inpElemsInParentTable[0];
			parentNodeChkBox.checked = checkUncheckSwitch;
			//do the same recursively
			CheckUncheckParents(parentNodeChkBox, checkUncheckSwitch);
		}
	}
}
function AreAllSiblingsChecked(chkBox) {
	var parentDiv = GetParentByTagName("div", chkBox);
	var childCount = parentDiv.childNodes.length;
	for (var i = 0; i < childCount; i++) {
		if (parentDiv.childNodes[i].nodeType == 1) //check if the child node is an element node
		{
			if (parentDiv.childNodes[i].tagName.toLowerCase() == "table") {
				var prevChkBox = parentDiv.childNodes[i].getElementsByTagName("input")[0];
				//if any of sibling nodes are not checked, return false
				if (prevChkBox != null && !prevChkBox.checked) {
					return false;
				}
			}
		}
	}
	return true;
}
//utility function to get the container of an element by tagname
function GetParentByTagName(parentTagName, childElementObj) {
	var parent = childElementObj.parentNode;
	while (parent.tagName.toLowerCase() != parentTagName.toLowerCase()) {
		parent = parent.parentNode;
	}
	return parent;
}