Hi Claus,

Welcome to the OutSystems Community!
I'll assume here, since you're new to this technology, that you have been going thru the online training, my answer will include concepts you can learn on your own with this training. If you haven't seen the online training I strongly encourage you to do so...

The sorting functionality is performed at database level, i.e. when you sort by a column the query that retrieves data and displays it in the screen is re-executed and its results are again bound to the widget on the screen. This means that the selections you did on the checkboxes (and that were only in memory and not stored in the database) are lost.

Now, the solution really depends on what you want to do but, coming to your question, you can implement an action that is triggered when the selection of the checkbox changes, that would be the OnCheckBoxChange you mention.

Every input on the screen must be bound to a variable, it is this variable that stores the value of the user input and in the case of the checkbox this is a boolean variable. So to validate if the checkbox is selected or not you must test the variable and not the widget. In the case that the checkbox is in a TableRecords widget surely you have a boolean attribute in the query the fills this TableRecords and that is the variable bound to the checkbox. That is the variable you want to test!

Cheers

Ok, I understand. Thanks. Yes, I have a variable that the checkbox is bound to:
DecisionModel.Selected - and it is a boolean.
I've implemented OnCheckBoxChange.
I thought I would be assigning "DecisionModel.Selected = widget.checkbox.value"
But what exactly will I have to do in the OnCheckBoxChange action to ensure that the database is updated?

Depends...
Can you detail more what you want to do or attach an example. If you wish to attach your eSpace module to the post you can export it from the development environments using Ctrl+S.

I simply want to avoid that the checkbox selections are cleared when the listbox is resorted (by clicking one of the other columns). I have tied a variable "Selected" to the checkbox. It is correctly set to true or false when the checkbox is selected. However, if I resort the columns, all the checkboxes are cleared.
This doesn't seem to be the default behavior, you would want.

Unfortunately due to the nature of web applications that is not that easy :(
Let me try to give you some guidance, but let me warn you that this might be complex for a newbie...

First of all you need to be aware that this solution should not be used when you have a large list of elements to select from. To keep the selections you'll need to keep everything in memory and also sort the list in memory. For that you'll need to use this component.

Check the attached example and the reminders inside for help.

Cheers

Thanks - I will check it out!