I am using combobox control, when I delete characters It throws the same error **IndexOutOfRangeException**

[tznind]

I am using combobox control, when I delete characters It throws the same error IndexOutOfRangeException

Originally posted by @ttool22 in https://github.com/gui-cs/Terminal.Gui/issues/1250#issuecomment-1211739635

[tznind]

@ttool22 I have moved the discussion to a new issue because the one you posted in is about scroll view. So while the Exception is the same (IndexOutOfRangeException) the root cause is likely to be different.

[tznind]

I've created a new console project with a combo box and it is working fine in 1.7.2

using Terminal.Gui;

Application.Init();

var w = new Window();

ComboBox combobox1 = new ComboBox();
combobox1.SetSource(new List<string> { "cow", "dog", "fish" });
combobox1.Width = 10;
combobox1.Height = 4;
w.Add(combobox1);

Application.Run(w);

Application.Shutdown();

Can you provide more information about how your use case varies from the above?

• Do you have any event handlers?
• Do you ever change the source of the combo box? (e.g. from another Thread or in a callback)

One thing that might help is if you can get a stack trace. The easiest way to do this is to add an Exception handler to the main loop. To do that you can swap Application.Run(myWindow) to use the overload:

Application.Run(myWindow, (e) =>
        { 
            MessageBox.ErrorQuery("Badness", e.ToString(), "Ok");
            return false;
        }
        );

If you implement the above block you should get an error box instead of a hard crash:

Example error message shown by registering an Exception callback

[ttool22]

Yes, I have event handler for refreshing time every second. I call eventhandler for refreshing time in OpenSelectedItem

timer.Elapsed += RefreshMatchTime; timer.Start();

static void RefreshMatchTime(object sender, ElapsedEventArgs e) { MatchTime.Text = DateTime.Now.Second.ToString(); Application.Refresh(); }

[tznind]

Ok thanks for the info. I think I am able to reproduce your error. Here is my repro:

using System.Timers;
using Terminal.Gui;

Application.Init();

var w = new Window();

ComboBox combobox1 = new ComboBox();
combobox1.SetSource(new List<string> { "cow", "dog", "fish" });
combobox1.Width = 10;
combobox1.Height = 4;
w.Add(combobox1);

// I have changed this to every 100th of a second to make the Exception manifest faster
var timer = new System.Timers.Timer(10);
timer.Elapsed += (s, e) => {
    combobox1.Text = DateTime.Now.Second.ToString();
    Application.Refresh();
};
timer.Start();


Application.Run(w, (e) =>
        { 
            MessageBox.ErrorQuery("Badness", e.ToString(), "Ok");
            return false;
        }
        );

Application.Shutdown();

The solution is to always use Application.MainLoop.Invoke to update UI properties. Please can you try updating your RefreshMatchTime method to use invoke:

var timer = new System.Timers.Timer(100);
timer.Elapsed += (s, e) => {
    Application.MainLoop.Invoke(()=> { combobox1.Text = DateTime.Now.Second.ToString(); });
};

Make sure to get rid of your call to Application.Refresh(); too.

After applying the fix (MainLoop.Invoke)

[tznind]

@ttool22 let me know if my suggestion works. Alternatively if you haven't understood what I have said or how to implement it please say and I will try to rephrase.

If you do get it working make sure to close the issue as resolved

[ttool22]

@tznind

Unfortunately it doesn't work

[tznind]

Can you share more of your code please? including the bit you updated with Application.MainLoop.Invoke

[ttool22]

timer.Elapsed += RefreshMatchTime; timer.Start();

static void RefreshMatchTime(object sender, ElapsedEventArgs e)
{
    try
    {
        string matchTime = string.Empty;        
        Constants.Seconds = Constants.Seconds + 1;
        matchTime = Constants.Minutes + " : " + (Constants.Seconds).ToString();

        Application.MainLoop?.Invoke(() =>
        {         
            Constants.MatchTime.Text = matchTime;
            Application.Refresh();
        });
    }
    catch (Exception ex)
    {

    }
}

[ttool22]

I call it inside

ComboboxControl.OpenSelectedItem += async (ListViewItemEventArgs control) =>
{
  //code above
}

}

[ttool22]

You didn't call it inside ComboboxControl.OpenSelectedItem, When I click on item in Combobox I start refresh time every second then I remove characters from combo, then error is thrown "IndexOutOfRangeEdxception"

[BDisp]

Remove Application.Refresh(); from the code because the Application.MainLoop?.Invoke already will update the UI Thread.

[tznind]

I have updated and changed the assignment to be a Label rather than the combo box as I assume you are using. It is still working as intended with no Exception.

The differences I can see vs your code are:

• I only create one timer (regardless of how many times user confirms selection)
• I don't call Application.Refresh (as @BDisp said)

using System.Timers;
using Terminal.Gui;

Application.Init();

var w = new Window();

Label matchTime = new Label();
matchTime.Width = 20;
matchTime.Height = 1;
matchTime.Y = 6;

ComboBox combobox1 = new ComboBox();
combobox1.SetSource(new List<string> { "cow", "dog", "fish" });
combobox1.Width = 10;
combobox1.Height = 4;

w.Add(combobox1);
w.Add(matchTime);

System.Timers.Timer? timer = null;

/*I've added async keyword here because you have it in your code but it has no effect*/
combobox1.OpenSelectedItem += async (ListViewItemEventArgs control) =>
{
    // do not create multiple timers
    if(timer == null)
    {
        timer = new System.Timers.Timer(10);
        timer.Elapsed += (s, e) =>
        {
            Application.MainLoop.Invoke(() => { matchTime.Text = DateTime.Now.Second.ToString(); });
        };
    }
    timer.Start();
};

Application.Run(w, (e) =>
        { 
            MessageBox.ErrorQuery("Badness", e.ToString(), "Ok");
            return false;
        }
        );

Application.Shutdown();