pushp

In a lot of scenarios it is required to get the value of a treenode (for an asp.net treeview) on the client side. While on the server we can get the nodevalue directly via the Value property of the Treenode, on the client it seems there is no corresponding attribute added to the anchor(yes treenodes are rendered as anchor(<a ..) tags) . Getting the node’s text is easy – just get hold of the node’s anchor element and call its innerText property. But how do we get the node value? Well, if you look closely at the rendered HTML for the node, you could find the node value lurking inside the href property for the node (provided you have not set the NavigateUrl property for the node manually). Something like:

href=”javascript:__doPostBack(‘TreeView1′,’sRoot\\firstChild\\…\\nodeValue‘)”

All we have to do is to extract that bold part from what the href property gives us.
Whereas there may be various scenarios where we may need the node value on the client, I would demonstrate it for the case of the node click itself – you want the value when you click a treenode. Try this:

1) Add an attribute to the treeview in code behind as:

if (!IsPostBack)
{
TreeView1.Attributes.Add(“onclick”, “return OnTreeClick(event)”);
}

2) Put the below code in head tag of .aspx page

<script type=”text/javascript”>
function OnTreeClick(evt)
{
var src = window.event != window.undefined ? window.event.srcElement : evt.target;
var nodeClick = src.tagName.toLowerCase() == “a”;
if(nodeClick)
{
var nodeText = src.innerText;
var nodeValue = GetNodeValue(src);
alert(“Text: “+nodeText + “,” + “Value: ” + nodeValue);
}
//return false; //uncomment this if you do not want postback on node click
}
function GetNodeValue(node)
{
//node value
var nodeValue = “”;
var nodePath = node.href.substring(node.href.indexOf(“,”)+2,node.href.length-2);
var nodeValues = nodePath.split(“\\”);
if(nodeValues.length > 1)
nodeValue = nodeValues[nodeValues.length - 1];
else
nodeValue = nodeValues[0].substr(1); return nodeValue;
}
</script>

Another scenario i can think of is when you have check boxes in the treeview and you want to get the nodevalue for the node that is checked. In that case you can just get the checkbox ( rendered as input tag) element first and then you can get the reference to the node via the nextSibling property for the checkbox.

That’s all. Hope this is helpful.

pushp

Its a very common requirement to have the parent-child check behaviour in asp.net treeview. To define the problem:
1)Check all the child nodes if the parent is checked and uncheck all child nodes if parent is unchecked ( well, this part is simple).
2)If a node at any level is checked and all its siblings are already checked then the parent node should be checked and the same should apply for the parent node(i.e., if its siblings are checked….), this should happen till the root node.
3)If a node at any level is unchecked then the parents( ma, grand ma, grand grand ma….) up to the root node must be unchecked.

Well there have been scripts on the net that only half accomplished the task(check footnotes). So I wrote the script that solves the problem completely, upto best of my knowledge. I’ve tested in IE 7 and Firefox 2.0, hope it works fine for you all.

Here’s how to implement it:

Step 1: In the page load in code behind file add an attribute to the treeview as:

If(!isPostBack)
{
TreeView1.Attributes.Add(“onclick”,”OnTreeClick(event)”);
}

The desired affect could also be accomplished by direclty adding the attribute to the treeview tag in .aspx file as: <asp:treeview onclick=”OnTreeClick(event)”… which would cause Visual Studio to display a warning but it works anyway but the codebehind way of doint it is the right way.

Step 2: Put the below script in the head section of your .aspx page:

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;
//check if nxt sibling is not null & is an element node
if(nxtSibling && nxtSibling.nodeType == 1)
{
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<checkBoxCount;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.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;
}

Get Formatted Version Of Above Script

The script is pretty much self explanatory with function names saying it all.
Comments awaited.

Footnotes: There has been other scripts on the net that accomplished the job only partially, the one that reached closest to doing it could be found in this thread on asp.net forums, i too have posted my solution there.

Hope this is helpful.

pushp

The asp.net treeview provieds a lot of features/functions, one of which is the Expand/Collapse All functionality on the server side. The Treeview Control has got two function for doing just that:
TreeView.ExpandAll(), TreeView.CollapseAll(). But going to server to accomplish such a simple functionality seemed a little odd to me. So, I wrote some javascript to do the same on the client.
Checkout the below script:

function TreeviewExpandCollapseAll(treeViewId, expandAll)
{
var displayState = (expandAll == true ? “none” : “block”);
var treeView = document.getElementById(treeViewId);
if(treeView)
{
var treeLinks = treeView.getElementsByTagName(“a”);
var nodeCount = treeLinks.length;
var flag = true;for(i=0;i<nodeCount;i++)
{
if(treeLinks[i].firstChild.tagName)
{
if(treeLinks[i].firstChild.tagName.toLowerCase() == “img”)
{
var node = treeLinks[i];
var level = parseInt(treeLinks[i].id.substr(treeLinks[i].id.length – 1),10);
var childContainer = GetParentByTagName(“table”, node).nextSibling;if(flag)
{
if(childContainer.style.display == displayState)
{
TreeView_ToggleNode(eval(treeViewId +”_Data”),level,node,’r',childContainer);
}
flag = false;
}
else
{
if(childContainer.style.display == displayState)
TreeView_ToggleNode(eval(treeViewId +”_Data”),level,node,’l',childContainer);
}
}
}
}//for loop ends
}
}//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;
}

Get Formatted Version Of Above Script

The above script could be used as:

<a href=”javascript:TreeviewExpandCollapseAll(‘<%=TreeView1.ClientID%>’, true)”>Expand All</a>
<a href=”javascript:TreeviewExpandCollapseAll(‘<%=TreeView1.ClientID%>’, false)”>Collapse All</a>
<asp:TreeView ID=”TreeView1″ …………………

That’s all there is to it.

Hope this is helpful.

pushp