ERROR in Threading using Timer and Data

Question

I have implemented a delay in process after the user stops typing in the textbox

private System.Timers.Timer timer = new System.Timers.Timer(1000);

public SearchItem(){
    timer.AutoReset = false;
    timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed);
}

private void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e){
        bindingSource.DataSource = logic.GetData(StockCodeTextBox.Text);
}

private void StockCodeTextBox_TextChanged(object sender, EventArgs e){
        timer.Stop();
        timer.Start();

        if (StockCodeTextBox.Text.Equals("")){
            AllItemsGridView.ClearSelection();
            return;
        }
}

after the user stops typing, why am I getting this error?

An exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll but was not handled in user code

Additional information: Cross-thread operation not valid: Control 'AllItemsGridView' accessed from a thread other than the thread it was created on.

You are using WPF right? And you are getting the error in the timer_Elapsed method? — Jens, Mar 03 '15 at 13:21
possible duplicate of [WPF and cross thread operations](http://stackoverflow.com/questions/2172229/wpf-and-cross-thread-operations) — , Mar 03 '15 at 13:28

Darek · Accepted Answer · 2015-03-03T13:42:09.167

3

Your UI is updated on the WinForms UI Dispatcher thread, while your Timer executes on a background thread. So you can't update the UI from a thread which does not own it. One workaround is to use this extension to update your UI from background thread:

public static class ControlExtension
{
    public static void Do<TControl>(this TControl control, Action<TControl> action)
    where TControl : Control
    {
        if (control.InvokeRequired)
            control.Invoke(action, control);
        else
            action(control);
    }
}

Sample use:

this.Do(f=>{f.AllItemsGridView.ClearSelection();})

In your code:

private void StockCodeTextBox_TextChanged(object sender, EventArgs e){
    timer.Stop();
    timer.Start();

    this.Do(f=>{
        if (f.StockCodeTextBox.Text.Equals("")){
            f.AllItemsGridView.ClearSelection();
        }
    }
}

private void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e){
    this.Do(f=>{ 
       f.bindingSource.DataSource = logic.GetData(f.StockCodeTextBox.Text);
    }
}

If you are free to choose a solution, consider rewriting your app with ReactiveUI and .Net 4.5.2. https://github.com/AdaptiveConsulting/ReactiveTrader

edited Mar 03 '15 at 13:42

answered Mar 03 '15 at 13:26

Darek

4,687
31
47

1

It would be nice if you add a reason why to execute the action on the UI-thread :) Reading the question indicates that the OP doesn't know anything regarding this issue ... – Mar 03 '15 at 13:27
It's magic, @Rjmr ... :) Kidding aside, the extension simply extends any `Control` to have an extra method, wonderful isn't it? A `Form` derives from a `Control` so every form gets a new method, `Do`, which checks if the operation passed into it, the stuff in-between the curly brackets, should execute on the thread it arrived on, or if it should be redirected to the UI thread. Makes sense? – Darek Mar 03 '15 at 13:34
1

i think in his code it should be: `this.Do(f=>{ bindingSource.DataSource = logic.GetData(StockCodeTextBox.Text); }` – Jens Mar 03 '15 at 13:37
thanks for letting me understand. But, i still have few questions on my mind. where would i put this line of code? `bindingSource.DataSource = logic.GetData(StockCodeTextBox.Text);` – Rjmr Mar 03 '15 at 13:38
Updated with a sample, but you should really, really consider ReactiveUI. Makes this whole thing soooo much simpler. – Darek Mar 03 '15 at 13:40
1

thank you so much guys for helping me with this one. if you have any suggestions on what topic/s should i study more, please comment it here. thanks again. – Rjmr Mar 03 '15 at 13:52

score 0 · Answer 2 · answered Mar 03 '15 at 13:23

0

If you are using System.Windows.Forms, you should use the Timer that comes with it so you don't have cross threading issues.

Instead of System.Timers.Timer use System.Windows.Forms.Timer.

answered Mar 03 '15 at 13:23

nvoigt

75,013
26
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that's not the problem. it's a problem of wpf updating the UI. He needs to use the Dispatcher in the `bindingSource.DataSource = logic.GetData(StockCodeTextBox.Text);` line i think. – Jens Mar 03 '15 at 13:27
2

@JensHorstmann Why do you assume WPF when the error message clearly says it's WinForms? – nvoigt Mar 03 '15 at 13:29
because i had this exception with the same problem in wpf - that's why. – Jens Mar 03 '15 at 13:31
i may be wrong with wpf, but it seems to be the same with Win Forms ;) – Jens Mar 03 '15 at 13:32
i am getting error in the timer_Elapsed method sir. – Rjmr Mar 03 '15 at 13:32

ERROR in Threading using Timer and Data

2 Answers2