Develop Reference

Why does my timer not stop when checkbox is unchecked?

Here's my code
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
System.Timers.Timer myTimer = new System.Timers.Timer();
myTimer.Elapsed += new ElapsedEventHandler(DisplayTimeEvent);
myTimer.Interval = Convert.ToInt32(textBox5.Text);
if (checkBox1.Checked)
{
myTimer.Start();
}
else
{
myTimer.Stop();
}
}
It should stop repeating the function when unchecked, but it doesn't. What's wrong with it?

I recommend that you stop using System.Timers.Timer and start using a System.Windows.Forms.Timer component.
Begin by removing your myTimer-related code (the entire body of checkBox1_CheckedChanged will need to be replaced with code from below.)
Add a Timer component to your form using the designer and name it myTimer. This will add a System.Windows.Forms.Timer field to your form called myTimer.
Using the designer, set the Tick event handler of myTimer to DisplayTimeEvent. (Or add a new handler and replace its code with the code of your DisplayTimeEvent function.)
Then change your checkBox1_CheckedChange function to look like this:
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
if (int.TryParse(textBox5.Text, out int interval)) {
this.myTimer.Interval = interval;
}
this.myTimer.Enabled = checkBox1.Checked;
this.textBox5.Enabled = !checkBox1.Checked;
}
I also recommend adding the following handler to textBox5 to perform the bare minimum validation so you can't crash your app by entering an interval of 0 or the empty string, or some text that is not an integer.
private void textBox5_TextChanged(object sender, EventArgs e)
{
this.checkBox1.Enabled = (int.TryParse(textBox5.Text, out int interval) && interval > 0);
}
The System.Windows.Forms.Timer's Tick handler will be called in the UI thread, meaning it will be safe to do things like update labels of your form in that handler. In contrast to that, the System.Timers.Timer will be called on a worker thread and will require that you take on some some thread-management responsibilities you likely don't want to incur, such as invoking your UI updates back to the main UI thread. See Why there are 5 Versions of Timer Classes in .NET? for more info.

Everytime checkbox1 is changed, new Timer is created. When checkbox is ticked, created timer is active and will invoke DisplayTimeEvent forever. When checkbox is unticked, you stop another Timer, which was just created.
You need to create Timer only once (probably when form is created), or when checkbox1 is changed first time:
private System.Timers.Timer myTimer;
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
if (myTimer == null) {
myTimer = new System.Timers.Timer();
myTimer.Elapsed += new ElapsedEventHandler(DisplayTimeEvent);
myTimer.Interval = Convert.ToInt32(textBox5.Text);
}
if (checkBox1.Checked)
{
myTimer.Start();
}
else
{
myTimer.Stop();
}
}

Visual Studio C# using timer to hold down the program for 1 hour

I am a new user and i wish to add a timer to hold down the program for an hour and then continues.
This is the procedure:
Issue a command through serialport e.g. high
Holds for an hour
Issue again the same command 'high'
Holds for an hour
It repeats until a button is pressed.
How should i implement the timer? Because i tried searching online and found some examples.
I included this in Form1.cs:
static System.Timers.Timer Timer1;
void button1_Click(object sender, EventArgs e)
{
Timer1 = new System.Timers.Timer(60*60*1000);
Timer1.Elapsed += new ElapsedEventHandler(TimedEvent);
Timer1.Enabled = true;
}
private void TimedEvent(Object source, ElapsedEventArgs e)
{
serialPort1.Write("high");
}
Even though this code helps to repeat the high every hour but it only does the TimedEvent after 60 minutes. I need to write into the serialport first then execute the timer. How do i amend the codes to achieve the result i want?
Edited:
I realised that this code does not work as in the timer did not hold for an hour. Instead place it in form1_load to work.
private void Form1_Load(object sender, EventArgs e)
{
Timer1 = new System.Timers.Timer(10*1000);
Timer1.Elapsed += TimedEvent;
}
Tried this (below) but the timer didn't work
static System.Windows.Forms.Timer timer4 = new System.Windows.Forms.Timer();
void button1_Click(object sender, EventArgs e)
{
Writetoserialport();
timer4.Interval = 10000; // testing on 10second interval
timer4.Enabled = true;
}
When i remove Writetoserialport() , the program runs forever.

Call TimedEvent directly for the first run:
private void Form1_Load(object sender, EventArgs e)
{
Timer1 = new System.Timers.Timer(10*1000);
Timer1.Elapsed += TimedEvent;
TimedEvent();
}
But for something that happens as rare as hourly, a Windows Service might be a better option.

This will work but will probably crash when you close the program sometimes because System.Timers.Timer triggers the TimedEvent on a ThreadPool thread. What will probably happen sometimes is when your program is closed, the SerialPort object will be disposed, but since the Timer is still executing on on another thread it will trigger the TimedEvent and try and write to the serialPort but it will crash the program because it will have been disposed.
You should look at System.Windows.Forms.Timer which is meant for using with GUI threads like this.
// INSTEAD, TRY THIS.
// It's really late here forgot to change some code after copy pasting from
above, should be good now.
static System.Windows.Forms.Timer timer1;
void button1_Click(object sender, EventArgs e)
{
timer1 = new System.Windows.Forms.Timer(60*60*1000);
timer1.Tick += Timer1_Tick;
timer1.Enabled = true;
WriteToSerialPort(); // Call method directly for writing to port.
}
private void timer1_Tick(object sender, EventArgs e)
{
WriteToSerialPort();
}
private void WriteToSerialPort()
{
serialPort1.Write("high"); // write to port
}

Here is another example that allows you to not have a dedicated method for writing to the serial port. I would want the dedicated method so the serial port could be written to outside of the timer tick event without having to write the serial port code more than once. The code below needs to be in try...catch blocks. Note: System.Windows.Forms.Timer here.
using System;
using System.Drawing;
using System.IO.Ports;
using System.Windows.Forms;
namespace SerialPortSample
{
public partial class Form1 : Form
{
private Timer timer1 = new Timer { Interval = 1000, Enabled = false }; // initialize timer, with a one second interval and disabled
private Button startTimerButton = new Button { Name = "startTimerButton",Text = #"Toggle Timer", Size = new Size(130, 33), Location = new Point(0, 0) };
// This is a place holder for the SerialPort control you probably have on your Form.
//Remove this instance of serialPort1 and use the serialPort1 control from your form.
private SerialPort serialPort1 = new SerialPort();
public Form1()
{
InitializeComponent();
// add button to Form
this.Controls.Add(startTimerButton); // add button to form1
startTimerButton.Click += StartTimerButton_Click;
timer1.Tick += Timer1_Tick; // attach timer tick event
}
private void StartTimerButton_Click(object sender, EventArgs e)
{
timer1.Enabled = !timer1.Enabled; // toggle timer.endabled, if false the Tick event will not be raised
timer1.Interval = 1000; // set timer interval to 1000 so the next time it is enabled it triggers immediately.
}
private void Timer1_Tick(object sender, EventArgs e)
{
timer1.Interval = 60 * 60 * 1000; // set timer interval to 1 hour so it will not trigger for an hour
if (!serialPort1.IsOpen)
serialPort1.Open(); // open serial port if not open
serialPort1.Write("high"); // write to the serial port
serialPort1.Close(); // close serial port
}
}
}

How to wait for a button to be clicked?

After a button is clicked in a Windows form application written in C#, how to wait for another button to be clicked? Meanwhile I am updating a datagridview dynamically by current information.
EDIT
After button1 is clicked, I want to repeatedly update a dataGridView with current information and when button2 is clicked I want to stop updating the dataGridView.

Use Timer Class.
public partial class Form1 : Form
{
System.Windows.Forms.Timer timer;
public Form1()
{
InitializeComponent();
//create it
timer = new Timer();
// set the interval, so it'll fire every 1 sec. (1000 ms)
timer.Interval = 1000;
// bind an event handler
timer.Tick += new EventHandler(timer_Tick);
//...
}
void timer_Tick(object sender, EventArgs e)
{
//do what you need
}
private void button1_Click(object sender, EventArgs e)
{
timer.Start(); //start the timer
// switch buttons
button1.Enabled = false;
button2.Enabled = true;
}
private void button2_Click(object sender, EventArgs e)
{
timer.Stop(); //stop the timer
// switch buttons back
button1.Enabled = true;
button2.Enabled = false;
}
From MSDN:
A Timer is used to raise an event at user-defined intervals. This
Windows timer is designed for a single-threaded environment where UI
threads are used to perform processing. It requires that the user code
have a UI message pump available and always operate from the same
thread, or marshal the call onto another thread.
When you use this timer, use the Tick event to perform a polling
operation or to display a splash screen for a specified period of
time. Whenever the Enabled property is set to true and the Interval
property is greater than zero, the Tick event is raised at intervals
based on the Interval property setting.

So you have button A and button B. When button A is pressed you want to wait for button B to be pressed, then do something special? Without more information the simplest way is something like this:
private void OnButtonAClicked(object sender, EventArgs e)
{
ButtonA.Enabled = false;
ButtonA.Click -= OnButtonAClicked;
ButtonB.Click += OnButtonBClicked;
ButtonB.Enabled = true;
}
private void OnButtonBClicked(object sender, EventArgs e)
{
ButtonB.Enabled = false;
ButtonB.Click -= OnButtonBClicked;
// Do something truly special here
ButtonA.Click += OnButtonAClicked;
ButtonA.Enabled = true;
}
This code will toggle(initial state; button A is enabled, button B is disabled), when button A is pressed, button B becomes enabled and processes events, etc.

Use the BackgroundWorker http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx
It doesn't freeze the UI, support ProgressBar, also it can be async. At the link you will see a good example with same functional that you want (start some task by click on one button and cancel it by click on another button).

Making a control to be visible only for a particular amount of time in c#

I am developing an application where i need the following requirement:
Suppose i have a button and a label (initially visibility set to false) in my form, and user clicks on the button, then the label should be displayed with some text that i assign to the label in the button click. But this label should be displayed only for some time, say some 3 secs and then it should automatically go invisible. For this if i gave:
private void button1_Click(object sender, EventArgs e)
{
label1.Visible=true;
label1.Text= "Magic";
Thread.Sleep(3000);
label1.Visible=false;
}
This code does not help the purpose. What is the approach to do it?

Try replacing the last two lines of your method with this:
System.Windows.Forms.Timer timer = new System.Windows.Forms.Timer();
timer.Interval = 3000;
timer.Tick += (source, e) => {label1.Visible = false; timer.Stop();};
timer.Start();
Using Thread.Sleep() is never a good idea in WinForms; use timers instead.

Create a timer with 3s as Interval, start it, and set Visible to false in your timer Tick event. Also don't forget to stop the timer.
Never call Thread.Sleep in your UI thread: the application will be blocked as the UI thread won't accept messages (user click...) while sleeping.

// create a global _timer object
static Timer _timer; // From System.Timers
private void button1_Click(object sender, EventArgs e)
{
label1.Text = "Magic";
// Thread.Sleep(3000); // don't do Thread.Sleep()!
label1.Visible = false;
Start();
}
static void Start()
{
label1.Visible = true;
_timer = new Timer(3000); // Set up the timer for 3 seconds
_timer.Elapsed += new ElapsedEventHandler(_timer_Elapsed);
_timer.Enabled = true; // Enable it
}
static void _timer_Elapsed(object sender, ElapsedEventArgs e)
{
label1.Visible = false;
_timer.Stop();
}

Use Timer, perhaps Windows.Forms.Timer. You may have to play with enabling and disabling it when needed and not needed. Your current way does not help, coz your making the main UI thread to sleep. No use.

c# loop every minute - where to put the code?

Currently I'm moving from java to c# and I'm full of crazy questions.
I'm trying new things on a windows form application and now,I would like to create a loop wich is executing a code every 1 minute,the problem is that I have no idea where to put this code.
For example,the form structure is like:
using System;
namespace Tray_Icon
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
notifyIcon1.ShowBalloonTip(5000);
}
private void notifyIcon1_BalloonTipClicked(object sender, EventArgs e)
{
label1.Text = "Baloon clicked!";
}
private void notifyIcon1_BalloonTipClosed(object sender, EventArgs e)
{
label1.Text = "baloon closed!";
}
private void contextMenuStrip1_Opening(object sender, CancelEventArgs e)
{
}
private void option1ToolStripMenuItem_Click(object sender, EventArgs e)
{
//some code here
}
private void option2ToolStripMenuItem_Click(object sender, EventArgs e)
{
//some code here
}
private void option3ToolStripMenuItem_Click(object sender, EventArgs e)
{
label1.Text = "Option 3 clicked!";
}
private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e)
{
option1ToolStripMenuItem_Click(this, null);
}
private void closeToolStripMenuItem_Click(object sender, EventArgs e)
{
this.Close();
}
private void btnWrite_Click(object sender, EventArgs e)
{
//code here
}
}
}
Where should I put the loop code? :(
Thanks in advance for ANY replay!!!

Add a Timer to your form:
set its Interval property to 60000 (one minute in milliseconds) and Enabled to True:
and attach an event handler to the Timer.Tick event, e.g. by double-clicking the timer in the Forms designer:
private void timer1_Tick(object sender, EventArgs e)
{
// do something here. It will be executed every 60 seconds
}

You would have to add a timer, and set the interval to 1000 miliseconds, and in the OnTick event you add the code with your loop
Timer tmr = null;
private void StartTimer()
{
tmr = new Timer();
tmr.Interval = 1000;
tmr.Tick += new EventHandler<EventArgs>(tmr_Tick);
tmr.Enabled = true;
}
void tmr_Tick(object sender, EventArgs e)
{
// Code with your loop here
}

You can't put any loop code in here.
In your designer look for the Timer control. When you have that, configure it to run every minute and place your code in the Timer_Tick event.
Or create a timer manually in code and respond to the event :) But for starters, doing it by the designer is easier!

Drag a Timer component on the Form and doubleclick it. There you go with the code.
The Timer component runs in the main thread so you can modify UI components without worrying.
Alternatively You could create a System.Timers.Timer, which has it's own thread and has some advantages, but possible caveats when modifying UI components. See http://msdn.microsoft.com/en-us/library/system.timers.timer.aspx

Try to use Background Worker and put the code in the backgroundWorker.DoWork or use a Timer

Use System.Timers.Timer:
System.Timers.Timer aTimer;
{
aTimer = new System.Timers.Timer();
aTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
aTimer.Interval = 60000;
aTimer.Enabled = true;
}
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
Console.WriteLine("The Elapsed event was raised at {0}", e.SignalTime);
}
for using Timer see this tutorial: C# Timer

How you do it in Java platform?
I think Java should be the same with .net.
In fact, a form program is just normal program which contains a event dispatcher. The event dispatcher listen to the UI events and dispatch them to the event handlers. I think all the UI mode should like this, no matter Java or .net platform.
So generally speaking, you have 2 options:
Start the loop at beginning. In this case, you should insert your
code in the constructor of the Form.
Start the loop when user
click the button. In this case, you should insert your code in the
event handler function.
Yes, as others mentioned, you should use the timer. But this should after you know where your code should locate. You also can use a endless loop with a sleep call. But timer is a better solution.

Idea of timer is more better. But If you want to use threads. Then Follow this
Let me assume that You want to do it right from the start of program
You can write in body of function (event in fact) named Form1_Load as
Your actual code is just within while loop other code only to guide
I can guide if you don't know the use of threads in C#
bool button2Clicked = false;
private void Form1_Load(object sender, EventArgs e)
{
// A good Way to call Thread
System.Threading.Thread t1 = new System.Threading.Thread(delegate()
{
while (!button2Clicked)
{
// Do Any Stuff;
System.Threading.Thread.Sleep(60000); //60000 Millieconds=1M
}
});
t1.IsBackground = true; // With above statement Thread Will automatically
// be Aborted on Application Exit
t1.Start();
}