timers [Delay without Freezing the app !] C#

Question

I'm trying to make an application that every 10 minutes executes 10 different SQL queries, and between each SQL query there should be a short delay (for example, 1 second).

If I try to use Thread.Sleep(1000);, the other timers stop and the whole application freezes.

Any idea how to do this without freezing the application or stopping other timers?

Once you understand the fact that the timer you are using runs it's code on the UI thread this simply becomes a duplicate of any of the [many "UI Freezes" questions](http://stackoverflow.com/questions/5450353/c-sharp-alternative-to-thread-sleep) with the same solutions. — Scott Chamberlain, Jul 25 '13 at 18:02

Guvante · Answer 1 · 2013-07-25T21:21:07.353

5

You can use threading to spin up another thread which performs those actions.

The simplest form would be System.Threading.ThreadPool.QueueUserWorkItem(WaitCallback)

It takes a delegate which consumes a single object and performs the task.

e.g.

private void Worker(object ignored)
{
    //Run first query
    Thread.Sleep(1000);
    //Run second query etc.
}

//The following code is where you want to start the process
//For instance in response to a timer
ThreadPool.QueueUserWorkItem(Worker);

edited Jul 25 '13 at 21:21

answered Jul 25 '13 at 18:01

Guvante

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Well at first thank you. then i tried to put your code into my source as a test http://prntscr.com/1hh8ry as you can see there is a red mark under wait . any fix ? – ahmed tota 2006 Jul 25 '13 at 18:16
The method is called Sleep, not wait. I fixed it in the answer. – Florian Greinacher Jul 25 '13 at 18:18
this will freeze the app. – ahmed tota 2006 Jul 25 '13 at 18:19
1

Not if you trigger this method through `ThreadPool.QueueUserWorkItem` as suggested by Guvante. – Florian Greinacher Jul 25 '13 at 18:31
@ahmedtota2006: I expanded the answer to show the place where this method is "called". – Guvante Jul 25 '13 at 21:21

score 1 · Answer 2 · answered Jul 25 '13 at 18:01

1

For each timer's execute, you should start a new thread to execute your SQL Queries code.

answered Jul 25 '13 at 18:01

Adel Khayata

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score 0 · Answer 3 · answered Jul 25 '13 at 18:03

I think what you're saying is every 10 minutes you need to fire off 10 SQL queries, and you want a pause between each.

First question, do you want one to complete before the next starts and add 1 second between them? Or start each 1 second apart but all may be running at the same time?

And are you running these in your main UI thread (bad idea) or a worker thread?

Based on your question I think you're running them in your main thread. Instead create a worker thread that fires once every 10 minutes. Without the worker thread your system will freeze anytime a query takes awhile.

If you want 1 second between completion of one thread and start of the next, you can put the Sleep(1000) call in the worker thread.

If you want 1 second between the start of each, you need 10 worker threads. The first will set the second to fire in 1 second, then call it's query. The second will set the third to fire in 1 second, then start it's query.

timers [Delay without Freezing the app !] C#

3 Answers3