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timer doesn't contain definition of "change"

I have timer that starts counting when a certain event (someEvent) occurs for one second, if the event is fired again within this second I want the first timer to stop and starts counting again from 0 I tried this :
void someEvent (object sender, TextChangedEventArgs e )
{
aTimer = new System.Timers.Timer();
aTimer.Change(5000, 0);
aTimer.Elapsed += OnTimedEvent;
aTimer.AutoReset = true;
aTimer.Enabled = true;
}
timer definition in the MainWindow:
private System.Timers.Timer aTimer;
According to this C# Timer.Change Method
But I get an error over aTimer.Change saying: "timer doesn't contain a definition of 'Change'."
This was implemented using WPF.

Namespaces Matter
.NET has quite a few timers classes, each of which have their own specific functionality and exposed methods, so it can be easy to get confused between the namespaces (as most of the classes are just called Timer).
You are currently using the System.Timers.Timer class, which primarily consists of the Start() and Stop() methods. If you want the Change() method, you would need to instead use an instance of the System.Threading.Timer class :
// Declare the timer as the other type of timer
aTimer = new System.Threading.Timer();

Yours is a System.Timers.Timer. This timer does not have a Change Method
The Timer.Change() event is used in System.Threading.Timer Timer.Change

C# EvenHandler only updates once

I'm trying to get more familiar with eventhanlders, but my current even only updates once, I want it to update until I close the application.
This is my code:
private static event EventHandler Updater;
Updater += Program_updater;
Updater.Invoke(null, EventArgs.Empty);
Application.Run();
private static void Program_updater(object sender, EventArgs e)
{
KeyUtils.Update();
Framework.Update();
}
But like I said, it will only update once, I want it to update until I close my application. I know I can just do a While(true) but I rather not.

I think you want a Timer here:
Timer aTimer = new System.Timers.Timer(2000);
// Hook up the Elapsed event for the timer.
aTimer.Elapsed += Program_updater;
// Have the timer fire repeated events (true is the default)
aTimer.AutoReset = true;
// Start the timer
aTimer.Enabled = true;
Specify callback:
private void Program_updater(Object source, System.Timers.ElapsedEventArgs e)
{
KeyUtils.Update();
Framework.Update();
}
Now every 2 seconds (or specify any other interval) callback OnTimedEvent will be called.

It is absolutely normal that your event is fired only once because the application starts only once.
What you acctualy need is to set up a timer and do some work on its tick.
Please have a look on example in answer for that question Simple example of the use of System. Timers. Timer in C#

Well it only updates once since you only invoke it once (I don't really get the context where your code runs since you both declare a static variable and invokes it on the same scope which is impossible).
If you want something to occur periodically you should use Timer, or in some cases AutoResetEvent/ManualResetEvent.
EventHandlers should be used only when you work as event driven which mean you want your handler to invoke When something happens
Here an example for [System.Timers.Timer][2] with your handler:
//Invoke every 5 seconds.
Timer timer = new Timer(5000);
//Add your handler to the timer invocation list.
timer.Elapsed += Program_updater;
//Start the timer.
timer.Start();
Also you need Program_update's signature to look like that:
private void Program_updater(object source, ElapsedEventArgs e)

c# timer.elapsed?

I have included the System.Timers package, but when I type:
Timer.Elapsed; //its not working, the property elapsed is just not there.
I remember it was there in VB.NET. Why doesn't this work?

It's not a property. It's an event.
So you gotta provide an event handler that will execute every time the timer ticks. Something like this:
public void CreateTimer()
{
var timer = new System.Timers.Timer(1000); // fire every 1 second
timer.Elapsed += HandleTimerElapsed;
}
public void HandleTimerElapsed(object sender, ElapsedEventArgs e)
{
// do whatever it is that you need to do on a timer
}

Microsofts example.
http://msdn.microsoft.com/en-us/library/system.timers.timer.elapsed.aspx
Elapsed is an event and therefore requires an eventhandler.
using System;
using System.Timers;
public class Timer1
{
private static System.Timers.Timer aTimer;
public static void Main()
{
// Create a timer with a ten second interval.
aTimer = new System.Timers.Timer(10000);
// Hook up the Elapsed event for the timer.
aTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
// Set the Interval to 2 seconds (2000 milliseconds).
aTimer.Interval = 2000;
aTimer.Enabled = true;
Console.WriteLine("Press the Enter key to exit the program.");
Console.ReadLine();
}
// Specify what you want to happen when the Elapsed event is
// raised.
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
Console.WriteLine("The Elapsed event was raised at {0}", e.SignalTime);
}
}
/* This code example produces output similar to the following:
Press the Enter key to exit the program.
The Elapsed event was raised at 5/20/2007 8:42:27 PM
The Elapsed event was raised at 5/20/2007 8:42:29 PM
The Elapsed event was raised at 5/20/2007 8:42:31 PM
...
*/

The previous answers here are all correct, however with .net 6 / VS2022 now out and about nullability is big deal, and all the above answers will throw compiler warning CS8622.
The solution to this is to simply mark the source object as nullable in your callback function's parameters, like such:
...
var timer = new System.Timers.Timer(2000); // every 2000ms
timer.Elapsed += TimerElapsedHandler;
...
public void TimerElapsedHandler(object? source, ElapsedEventArgs e)
{
//Your Handling Code Here
}

You need an event handler, then after Enabling while assigning event handler and stop in your handler a condition
Timer = new System.Timers.Timer();
Timer.Elapsed += new System.Timers.ElapsedEventHandler(PageLoaded);
Timer.Interval = 3000;
Timer.Enabled = true;
...................
public void PageLoaded(object source, System.Timers.ElapsedEventArgs e)
{
// Do what ever here
if (StopCondition)Timer.Enabled = false;
}

What is the best way to implement a "timer"? [duplicate]

This question already has answers here:
How do you add a timer to a C# console application
(12 answers)
Closed 3 years ago.
What is the best way to implement a timer? A code sample would be great! For this question, "best" is defined as most reliable (least number of misfires) and precise. If I specify an interval of 15 seconds, I want the target method invoked every 15 seconds, not every 10 - 20 seconds. On the other hand, I don't need nanosecond accuracy. In this example, it would be acceptable for the method to fire every 14.51 - 15.49 seconds.

Use the Timer class.
public static void Main()
{
System.Timers.Timer aTimer = new System.Timers.Timer();
aTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
aTimer.Interval = 5000;
aTimer.Enabled = true;
Console.WriteLine("Press \'q\' to quit the sample.");
while(Console.Read() != 'q');
}
// Specify what you want to happen when the Elapsed event is raised.
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
Console.WriteLine("Hello World!");
}
The Elapsed event will be raised every X amount of milliseconds, specified by the Interval property on the Timer object. It will call the Event Handler method you specify. In the example above, it is OnTimedEvent.

By using System.Windows.Forms.Timer class you can achieve what you need.
System.Windows.Forms.Timer t = new System.Windows.Forms.Timer();
t.Interval = 15000; // specify interval time as you want
t.Tick += new EventHandler(timer_Tick);
t.Start();
void timer_Tick(object sender, EventArgs e)
{
//Call method
}
By using stop() method you can stop timer.
t.Stop();

It's not clear what type of application you're going to develop (desktop, web, console...)
The general answer, if you're developing Windows.Forms application, is use of
System.Windows.Forms.Timer class. The benefit of this is that it runs on UI thread, so it's simple just define it, subscribe to its Tick event and run your code on every 15 second.
If you do something else then windows forms (it's not clear from the question), you can choose System.Timers.Timer, but this one runs on other thread, so if you are going to act on some UI elements from the its Elapsed event, you have to manage it with "invoking" access.

Reference ServiceBase to your class and put the below code in the OnStartevent:
Constants.TimeIntervalValue = 1 (hour)..Ideally you should set this value in config file.
StartSendingMails = function name you want to run in the application.
protected override void OnStart(string[] args)
{
// It tells in what interval the service will run each time.
Int32 timeInterval = Int32.Parse(Constants.TimeIntervalValue) * 60 * 60 * 1000;
base.OnStart(args);
TimerCallback timerDelegate = new TimerCallback(StartSendingMails);
serviceTimer = new Timer(timerDelegate, null, 0, Convert.ToInt32(timeInterval));
}

How to stop a timer after it is done running?

I have a Console App and in the main method, I have code like this:
Timer time = new Timer(seconds * 1000); //to milliseconds
time.Enabled = true;
time.Elapsed += new ElapsedEventHandler(time_Elapsed);
I only want the timer to run once so my idea is that I should stop the timer in the time_Elapsed method. However, since my timer exists in Main(), I can't access it.

You have access to the Timer inside of the timer_Elapsed method:
public void timer_Elapsed(object sender, ElapsedEventArgs e)
{
Timer timer = (Timer)sender; // Get the timer that fired the event
timer.Stop(); // Stop the timer that fired the event
}
The above method will stop whatever Timer fired the Event (in case you have multiple Timers using the same handler and you want each Timer to have the same behavior).
You could also set the behavior when you instantiate the Timer:
var timer = new Timer();
timer.AutoReset = false; // Don't reset the timer after the first fire

A little example app:
static void Main(string[] args)
{
int seconds = 2;
Timer time = new Timer(seconds * 1000); //to milliseconds
time.Enabled = true;
time.Elapsed += new ElapsedEventHandler(MyHandler);
time.Start();
Console.ReadKey();
}
private static void MyHandler(object e, ElapsedEventArgs args)
{
var timer = (Timer) e;
timer.Stop();
}

I assume that you're using System.Timers.Timer rather than System.Windows.Forms.Timer?
You have two options.
First, as probably the best, is to set the AutoReset property to false. This should do exactly what you want.
time.AutoReset = false;
The other option is to call Stop in the event handler.

You may also use the System.Threading.Timer. Its constructor takes two time-related parameters:
The delay before the first "tick" (due time)
The period
Set the period to Timeout.Infinite to prevent from firing again.