ASP.NET TreeView CheckBox nodes Check/Uncheck Functionality using JavaScript

Just copy and paste the below JavaScript in you'r page header tags.

<script 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;

            }

        }

        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;

        }

    </script>