asp.net treeview checkbox selection

Great solution above, thanks a lot. I changed the Method CheckUncheckParents() to my preferences: When one of the childnode is checked, the parentnode will be also checked.

function OnTreeClick(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
        {
            checkUncheckSwitch = true;
        }
        else //checkbox unchecked
        {
            var isAllSiblingsUnChecked = AreAllSiblingsUnChecked(srcChild);
            if (!isAllSiblingsUnChecked)
                checkUncheckSwitch = true;
            else
                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 AreAllSiblingsUnChecked(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.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;
}

Since I had exactly the same problem as in the question, I had to change the solution to affect only child nodes.

<script language="javascript" type="text/javascript">
function OnTreeClick(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;
    }
}


//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;
}

private void CheckUnCheck(object sender)
        {
            if ((sender as TreeView).SelectedNode.Checked == true)
                foreach (TreeNode tr in (sender as TreeView).SelectedNode.ChildNodes)
                {
                    foreach (TreeNode child in tr.ChildNodes)
                        child.Checked = true;
                    tr.Checked = true;
                }
            else
                foreach (TreeNode tr in (sender as TreeView).SelectedNode.ChildNodes)
                {
                    foreach (TreeNode child in tr.ChildNodes)
                        child.Checked = false;
                    tr.Checked = false;
                }
        }