" int ans = 2;
private void Form1_Load(object sender, EventArgs e)
{
for (int i = 0; i <21; i++)
{
ans = 2;
label1.Text += i.ToString();
while (true)
{
if (ans == 1)
{
break;
}
}
}
}
private void button1_Click(object sender, EventArgs e)
{
ans = 1;
} "
this is a simple app
I want to print a number & then wait to the button to be clicked to break the while loop
but when I run the application , the form doesn't show .
"T think that the problem is the while (true)".
what to do?
Use a timer. Start the timer when the form loads. Each time it ticks, increment the number and display it. On button click, you just need to stop the timer.
private Timer _myTimer;
private int number = 0;
private void Form1_Load(object sender, EventArgs e)
{
_myTimer = new Timer();
_myTimer.Interval = 1; // 1 millisecond
_myTimer.Tick += new EventHandler(MyTimer_Tick);
_myTimer.Start();
}
// increments the number at timer tick
private void MyTimer_Tick(object sender, EventArgs e)
{
number ++;
// TODO: update UI here
}
// Stops the timer
private void button1_Click(object sender, EventArgs e)
{
_myTimer.Stop();
}
It's best to not use a loop here. Since this loop won't end you won't ever leave Form_Load and it won't display the form. If you were trying to do some task when the user clicks a button, why not move that logic to button1_Click
?
The correct way to implement such a task as you describe would be as such:
private EventWaitHandle ewh = new EventWaitHandle(false, EventResetMode.AutoReset);
private void Form1_Load(object sender, EventArgs e)
{
Task.Factory.StartNew(() =>
{
for (int i = 0; i < 26; i++)
{
ewh.WaitOne();
Action updateLable = () => label1.Text = "" + i;
label1.BeginInvoke(updateLable);
}
});
}
private void button1_Click(object sender, EventArgs e)
{
ewh.Set();
}
As you can see I've replaced your busy wait (while(true)) with a .Net wait handle .
One of the answers describes a timer that acts every millisecond - that is a busy wait of sorts.
This is what async/await is for. Mark your Load() event with "async", then "await" a Task that continues when a ManualResetEvent is triggered in the Button click handler:
private System.Threading.ManualResetEvent mre = new System.Threading.ManualResetEvent(false);
private async void Form1_Load(object sender, EventArgs e)
{
for (int i = 0; i < 21; i++)
{
label1.Text = i.ToString();
mre.Reset();
await Task.Factory.StartNew(() => { mre.WaitOne(); });
}
button1.Enabled = false;
label1.Text = "Done!";
}
private void button1_Click(object sender, EventArgs e)
{
mre.Set();
}
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