WinForms ComboBox with async business rule

[michaelcsikos]

I've just come across some weird behaviour with ComboBox, DropDownStyle = DropDown and an async rule.

If the AutoCompleteSource = ListItems and AutoCompleteMode = SuggestAppend it's selecting the first match automatically in the AutoCompleteSource drop-down, and then the caret moves back to the start, e.g.

type R
[rule completes]
ComboBox updates to Red
type e
ComboBox now shows eRed

If the AutoCompleteMode = None the caret moves to the start as you type a complete match, e.g.
type R
type e
type d
[caret now positioned before R]

Running the rule sync fixes it, however, in this case I really would prefer to run it async, so I dug deeper.

It turns out that if you set AutoCompleteSource = CustomSource and add the values to AutoCompleteCustomSource it works perfectly.

EDIT: However, you lose the ability to click the drop-down button, of course...

[rockfordlhotka]

I hate to say it @michaelcsikos, but you may be one of the few who are still building new(ish) stuff on WinForms.

I'm totally willing to consider a new issue and PR for WinForms capabilities, but personally don't plan to spend time on WinForms.

[Chicagoan2016]

@rockfordlhotka I am the other one 😂
We have a huge Winforms application and it was much easier to write than another application with WPF UI.
The developer for WPF application didn't use any MVVM pattern but still tried to use the databinding in WPF. It's hell to maintain lol. In his defense, we had looked at Prism and as a small team we didn't have the time to integrate Prism with Csla.
The Winforms application on the other hand is a breeze to maintain. We have discussed this here #3770

[Chicagoan2016]

In this particular scenario, I can make the rule sync if the property is bound to a ComboBox, and async if using a TextBox.

@michaelcsikos How do you accomplish this, I mean changing rules from ASync to Sycn based on the UI control?
Regards

[rockfordlhotka]

I want to be clear.

In no way do I plan to stop having CSLA work with WinForms!! I expect we'll continue to maintain the existing functionality long into the future.

I think what I'm hearing here is that there's some issue that is caused by the fact that the world (and CSLA) have increasingly moved into an async model, while WinForms remains what it has always been - predating the whole async concept entirely.

I am very happy to have contributions to the Csla.Windows.Forms package that would help address this, if such a thing is possible.

[Chicagoan2016]

@rockfordlhotka, Thank you, Sir. I can't imagine developing an application without using Csla.
Kind Regards

[michaelcsikos]

In this particular scenario, I can make the rule sync if the property is bound to a ComboBox, and async if using a TextBox.

@michaelcsikos How do you accomplish this, I mean changing rules from ASync to Sycn based on the UI control? Regards

In this application we've designed a user-defined record type system. One of the options for text fields is to choose the control type: TextBox, ComboBox with style = DropDown (editable tex), or ComboBox with style = DropDownList (non-editable text).

If the Unique option has been switched on, the app checks if the value has been used in any other project, and if it has displays the number and name in the error provider. In the business rule I already know what control type will be used, so if it's TextBox I run the query async; if it's ComboBox it runs sync. You can still set the rule to be IsAsync = true but if you don't await anything it runs sync anyway, and the ComboBox behaves itself.