//************************** Treeview Parent-Child check behaviour ****************************// 
   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
            {
                var isAllSiblingsChecked = AreAllSiblingsChecked(srcChild);
                if(isAllSiblingsChecked)
                    checkUncheckSwitch = true;
                else   
                    return; //do not need to check parent if any child is 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.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;   
   }