Keeping UI responsive during a Thread.Sleep()

Question

Background: I am writing an application that iterates through a list of servers and obtains various details about each machine. During the iteration, I need to update various controls on the form (to display a summary of the obtained information). Because it is iterating through a list, I have called a Thread.Sleep() to allow the user time to read through the information before the next machine is interrogated. Below is my code:

Task TestTask = Task.Factory.StartNew(() =>
            {
                foreach (String IpAddress in ServersToCheck)
                {
                    if (IpAddress != String.Empty)
                    {
                        ServerBeingCheckedLabel.Text = IpAddress;
                        if (PingServer(IpAddress) == true)
                        {
                            PingChar_Label.ForeColor = Color.Green;
                            PingChar_Label.Text = "a";
                            CheckPermissionsAreValid(IpAddress);
                        }
                        else
                        {
                            PingChar_Label.ForeColor = Color.Red;
                            PingChar_Label.Text = "r";
                            PermChar_Label.ForeColor = Color.Red;
                            PermChar_Label.Text = "r";
                        }
                    }
                }
                Thread.Sleep(10000);
                this.BackColor = FormBackGroundColor;
                TestButton.Enabled = true;
                RunTimer.Enabled = true;
            }, CancellationToken.None, TaskCreationOptions.None, UiScheduler);

This works fine regarding updating the controls on the form, but during the Thread.Sleep() the UI locks up. Surely if the Thread.Sleep() is called on a separate task, the UI thread has remained unblocked?

score 5 · Accepted Answer · answered Aug 12 '15 at 08:54

5

Task.Delay should suit your needs.

Change

Task.Factory.StartNew(() =>

to

Task.Factory.StartNew(async () =>

and change

Thread.Sleep

to

await Task.Delay

answered Aug 12 '15 at 08:54

Dante May Code

11,177
9
49
81

This seems to work fine when the last details have been loaded, but doesn't seem to delay when running through items before this – Chris Wright Aug 12 '15 at 08:56
1

Never mind, I moved the await Task.Delay() to a different position and now it seems to be working like a charm. Thank you! – Chris Wright Aug 12 '15 at 08:58
@ChrisWright you are welcome. Remember to accept an answer if your question has been resolved. – Dante May Code Aug 12 '15 at 09:03
I'm just waiting on the time period to pass. Thanks again :) – Chris Wright Aug 12 '15 at 09:04

score 5 · Answer 2 · answered Aug 12 '15 at 08:54

If you pass the UiScheduler as TaskScheduler then that task is running on the UI thread. So yes, the UI thread is completely blocked when you call Thread.Sleep.

If you want to delay use await Task.Delay(10000) instead to delay asynchronously.

That will make the task returned from Task.Factory.StartNew a Task<Task> because it wasn't build with async-await in mind unlike Task.Run. To fix that use Task.Unwrap on the returned Task:

Task<Task> TestTask = Task.Factory.StartNew(async () =>
{
    // ...
    await Task.Delay(10000);
    // ...
}, CancellationToken.None, TaskCreationOptions.None, UiScheduler);

Task actualTask = TestTask.Unwrap();

Thanks very much for your input, unfortunately I can only mark one response as an answer :( — Chris Wright, Aug 12 '15 at 09:06

score 1 · Answer 3 · answered Aug 12 '15 at 08:53

1

use Task.Delay instead of Thread.Sleep checkout This link for more details

answered Aug 12 '15 at 08:53

santosh singh

27,666
26
83
129

Keeping UI responsive during a Thread.Sleep()

3 Answers3

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