Which C# pattern has better performance to avoid duplicated event handlers?

Which C# pattern has better performance to avoid duplicated event handlers?

By : Velhoo
Date : November 19 2020, 01:01 AM
I think the issue was by ths following , According the documentation, invocation list is being stored as array or something similar to it, and the order of the event handlers is being stored too. May be there are inner structure to maintain fast search for a particular method there.
So in the worst case operation of the GetInvocationList().Contains(MyEventHandlerMethod); is O(1) (as we simply got the reference for the array) + O(n) for searching the method, even if there is no optimization for it. I seriously doubt that this is true, and I think that there is some optimizing code, and it is O(log_n).
code :

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Avoid duplicated event handlers?

Avoid duplicated event handlers?

By : Bubnick
Date : March 29 2020, 07:55 AM
like below fixes the issue Wrapping the event handler list in a HashSet will make sure the handlers are not duplicate references, the following snippet replacement for the question's Item class will work under the above sample (it won't re-add the handler if it's already in the HashSet):
code :
Public Class Item
  Private m_Title As String
  Public Property Title() As String
      Return m_Title
    End Get
    Set(ByVal value As String)
      m_Title = value
      RaiseEvent TitleChanged(Me, EventArgs.Empty)
    End Set
  End Property

  Private handlers As New HashSet(Of EventHandler)

  Public Custom Event TitleChanged As EventHandler
    AddHandler(value As EventHandler)
    End AddHandler

    RemoveHandler(value As EventHandler)
    End RemoveHandler

    RaiseEvent(sender As Object, e As System.EventArgs)
      For Each handler In handlers.Where(Function(h) h IsNot Nothing)
        handler(sender, e)
    End RaiseEvent
  End Event
End Class
avoid event.preventDefault() boilerplate in backbone event handlers

avoid event.preventDefault() boilerplate in backbone event handlers

By : F.alam
Date : March 29 2020, 07:55 AM
around this issue Why do you need to have the href attribute at all, if you plan on discarding it anyway? How about just using a class name?
HTML code:
code :
<a class="makeCookies">Make Cookies</a>
'click .makeCookies': 'makeCookies'
makeCookies: function (event) {
    // No need for event.preventDefault() anymore!
How to avoid copy/paste many event handlers

How to avoid copy/paste many event handlers

By : James Jamerson
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further My application cannot access a specific menu item unless some condition is true (DataRepository.IsAllDataLoaded). I came up with this code, which works great. It checks for the condition first. If it is not ready, it calls a timer, which waits some milliseconds and call the same method again. The Timer needs an ElapsedEventHandler. , Use an anonymous lambda expression:
code :
WaitForDataLoading((s,e) => FirstMenuItem_Click(null, null));
Is there a performance penalty for binding multiple event handlers to the scroll event?

Is there a performance penalty for binding multiple event handlers to the scroll event?

By : user2453577
Date : March 29 2020, 07:55 AM
help you fix your problem I modified AlliterativeAlice's code after considering Bergi's comment. Using the native scroll event in Chrome I didn't see any significant difference in speed between the two approaches. Run the code below by copy and pasting into the JavaScript console of this web page, what results to you get?...
code :
function log() {
  console.log(Array.prototype.join.call(arguments, ' '))

var count100 = 0;
var count1 = 0;

function test100() {
  for (var i = 0; i < 100; i++) {
    $(window).on('scroll', function() {
  var startTime = performance.now();

  for (var x = 0; x < 100; x++) {
    window.scroll(0, 0);

    for (var j = 0; j < 100; j++) {
      window.scroll(0, j + 1);

  var endTime = performance.now();
  log("100 handlers: ", endTime - startTime);

function test1() {
  var count = 0;
  var fns = [];
  for (var i = 0; i < 100; i++) {
    fns.push(function() {

  $(window).on('scroll', function() {
    fns.forEach(function(f) {

  var startTime = performance.now();

  for (var x = 0; x < 100; x++) {
    window.scroll(0, 0);

    for (var j = 0; j < 100; j++) {
      window.scroll(0, j + 1);

  var endTime = performance.now();
  log("1 handler: ", endTime - startTime);

var testCount = 0;
var numberOfRuns = 20;

function logCount() {
  console.log("-->count1: ", count1);
  console.log("-->count100: ", count100);

function runTestA() {
  if (++testCount<numberOfRuns) setTimeout(runTestB, 10);
  else setTimeout(logCount, 10);

function runTestB() {
  if (++testCount<numberOfRuns) setTimeout(runTestA, 10);
  else setTimeout(logCount, 10);

Event handlers being duplicated when changing routes

Event handlers being duplicated when changing routes

By : mdavis
Date : March 29 2020, 07:55 AM
should help you out Event listener will never get removed directly, you need to remove them forcefully. You need to deregistered the listener while $destroying controller
code :
socket.forward('dataUpdate', $scope);
var socketEvent = $scope.$on('socket:dataUpdate', function(ev, data) {
   $scope.someVar1 = data;
   $scope.someVar2 = data;
   $scope.someVar3 = data;
   $scope.someVar4 = data;

$scope.$on('$destroy', function(){
   socketEvent(); //deregistering event while destroying controller scope.
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