表单应用程序C＃的无限while循环

Question

I need to run an infinite while loop when a form application starts. A form starts like this:

public Form1()
{
        InitializeComponent();
}

Now I want to run another function which will have an infinite loop inside with one second sleep time:

public void doProcess(){

    while(true){
         Thread.Sleep(1000);
         // other task
    }
}

How can I do this? When I call doProcess() in the constructor, it does not show the form. I tried to run the while loop for 10 iterations. The form showed up only after all the iterations are finished. I don't understand why it is happening.

Answer 1

In short, you are blocking the UI Thread with this infinite loop.

Run it async :

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        BeginWork();
    }

    private async void BeginWork()
    {
        while (true)
        {
            // Since we asynchronously wait, the UI thread is not blocked by the file download.
            var result = await DoWork(formTextField.Text);

            // Since we resume on the UI context, we can directly access UI elements.
            formTextField.Text = result;
        }
    }

    private async Task<string> DoWork(object text)
    {
        // Do actual work
        await Task.Delay(1000);
        // Return Actual Result
        return DateTime.Now.Ticks.ToString();
    }
}

A while(true) can be a bit excessive for an update loop. May I recommend that you potentially use a Timer, and/or leverage Cancellation Tokens to eagerly cancel requests which have taken too long as to not update UI with potentially stale results in high performance scenarios.

Eg

public partial class Form1 : Form
{
    private readonly Timer _sampleTimer;

    public Form1()
    {
        InitializeComponent();

        _sampleTimer = new Timer
            {
                Interval = 500 // 0.5 Seconds
            };
        _sampleTimer.Tick += DoWorkAndUpdateUIAsync;
    }

    private async void DoWorkAndUpdateUIAsync(object sender, EventArgs e)
    {
        // Since we asynchronously wait, the UI thread is not blocked by "the work".
        var result = await DoWorkAsync();

        // Since we resume on the UI context, we can directly access UI elements.
        resultTextField.Text = result;
    }

    private async Task<string> DoWorkAsync()
    {
        await Task.Delay(1000); // Do actual work sampling usb async (not blocking ui)
        return DateTime.Now.Ticks.ToString(); // Sample Result
    }

    private void startButton_Click(object sender, EventArgs e)
    {
        _sampleTimer.Start();
    }

    private void stopButton_Click(object sender, EventArgs e)
    {
        _sampleTimer.Stop();
    }
}

Answer 2

You can start a new thread like this:

new Thread(() => 
{
    while (true)
    {
        Thread.Sleep(1000);

        //other tasks
    }
}).Start();

Although I suggest you read up on threading before you do. If you want to update the form from a different thread you should use: Form.Invoke() .

For example: w is the form

 w.Invoke((MethodInvoker) delegate
 {
     w.Width += 100;
 });

Answer 3

It's happening because the ctor never exits and so the form cannot be shown - is this not obvious?

If you want to run a forever/sleep loop line this, you must thread it off.

Do not wait in GUI event handlers, (or ctors).

Can you not use forms.timer?

Answer 4

You are blocking the UI thread. Therefore, the UI cannot be processed as long as doProcess runs.

If you use .Net 4.5, you can use async waits:

public async void doProcess(){
    while(true){
         await Task.Delay(1000);
         // other task
    }
}

The cleaner solution would be to use a timer that fires an event every 1 second. You can turn off the timer after 10 loops.

Answer 5

You didn't exit the constructor so the form won't show. If you want to do it after form shows place your code in Form_Load event. But you rather want to do it using background thread so you can use backgroundworker

Answer 6

您可以将其放置在Initialize组件之后，或者找到表单的load事件，然后将代码粘贴到其中