Prevent/override standard Modal Dialog close button(X) from closing

Question

I want to validate custom modal dialog form and if its not ok, prevent form from closing. For this purpose, I attached to X-close-dialog-button. Problem is to prevent it's default behavior.

function fValidateBeforeClose(event) {
    event.stopImmediatePropagation(); // Not working
}    
function fAddOnCloseHandler() {
    var oCloseButton = jQuery("a[id^='DlgClose']", parent.document);
    oCloseButton.on( "click", function (event) { fValidateBeforeClose(event)} ); 
}       
_spBodyOnLoadFunctionNames.push( ExecuteOrDelayUntilScriptLoaded(fAddOnCloseHandler, "SP.js") );

Answer 1

Good way to remove handlers from dialog's close button is using $clearHandlers Method.

Check code below:

function fValidateBeforeClose(event) {
    var isValid = true;
    //set IsValid value
    if(isValid)
    {
       //close dialog
       SP.UI.ModalDialog.get_childDialog().close();
    }
    else
    {
      alert('Not valid');
    }
}  

function fAddOnCloseHandler() {
    var oCloseButton = $("a[id^='DlgClose']");

    $clearHandlers(oCloseButton.get(0));

    $(oCloseButton).on("click", function (event) { fValidateBeforeClose(event)} );
}   

_spBodyOnLoadFunctionNames.push( ExecuteOrDelayUntilScriptLoaded(fAddOnCloseHandler, "SP.js") );

Answer 2

In SharePoint 2013, this works fine after I added "window.parent.document" in the following line:

var oCloseButton = $("a[id^='DlgClose']",window.parent.document);

Answer 3

I think you should remove old event handler

 var js = oCloseButton.attr("onclick");
 oCloseButton.attr("onclick", "");//remove sharepoint click handler...