SYSK 325: How To Tell Which UpdatePanel Issued a Page PostBack
If you have multiple UpdatePanel controls on a page, and your Page_Load has a lot of data retrieval and rendering logic, you may want to know exactly which UpdatePanel is being updated, and execute only relevant code segments to optimize performance.
Here is a code snippet that should give you the UpdatePanel control id and the trigger control id that caused the postback.
Important: I’m relying on AJAX code (see below) that’s loaded at runtime as a resource (.axd) and it changes, this code might break.
if (Page.IsPostBack)
{
// Is it an AJAX postback?
foreach (string key in Request.Form.AllKeys)
{
if (key == ScriptManager.GetCurrent(this).ID)
{
string[] parameters = Request.Form[key].Split('|');
string updatePanel = parameters[0];
string ctrl = parameters[1];
break;
}
}
}
Here is the AJAX code I was referring to:
function Sys$WebForms$PageRequestManager$_getPostBackSettings(element, elementUniqueID) {
var originalElement = element;
var proposedSettings = null;
while (element) {
if (element.id) {
if (!proposedSettings && Array.contains(this._asyncPostBackControlClientIDs, element.id)) {
proposedSettings = this._createPostBackSettings(true, this._scriptManagerID + '|' + elementUniqueID, originalElement);
}
else {
if (!proposedSettings && Array.contains(this._postBackControlClientIDs, element.id)) {
return this._createPostBackSettings(false, null, null);
}
else {
var indexOfPanel = Array.indexOf(this._updatePanelClientIDs, element.id);
if (indexOfPanel !== -1) {
if (this._updatePanelHasChildrenAsTriggers[indexOfPanel]) {
return this._createPostBackSettings(true, this._updatePanelIDs[indexOfPanel] + '|' + elementUniqueID, originalElement);
}
else {
return this._createPostBackSettings(true, this._scriptManagerID + '|' + elementUniqueID, originalElement);
}
}
}
}
if (!proposedSettings && this._matchesParentIDInList(element.id, this._asyncPostBackControlClientIDs)) {
proposedSettings = this._createPostBackSettings(true, this._scriptManagerID + '|' + elementUniqueID, originalElement);
}
else {
if (!proposedSettings && this._matchesParentIDInList(element.id, this._postBackControlClientIDs)) {
return this._createPostBackSettings(false, null, null);
}
}
}
element = element.parentNode;
}
if (!proposedSettings) {
return this._createPostBackSettings(false, null, null);
}
else {
return proposedSettings;
}
}
