Hi Bostjan,
There where several errors. I changed your example, still using TIWBS4LayoutMgr. I think there are more possible solutions but this is a working one with v15.2.40
Main observation: Start using Chrome Developer Tools (F12) or similar. They give you lots of insights about what is happening and what is going wrong.
You have to use these tools to learn and build knowledge about IntraWeb. 'Google Is Your Best Friend'.
First thing DevTools showed was that several resources could not be found. You were using CDN by calling IWBS4LibSetCDNS so there seems an error in iwbootstrap4.
I e-mailed Alexandre and assume this gets fixed in a future release.
For the moment best thing to do is don't use CDN and host the resources yourself inside .\wwwroot folder. These ship as part of the IntraWeb installation under 'IntraWeb 15\Source\iwbootstrap4\redist'
Be aware that some errors, like typo's exist in this folder. Alexandre is aware of this as well.
But even after these changes the combobox was not working. An AV was generated after pressing button 'Add to Combo'.
Location of the AV was IWBSSelect1.OnHTMLTag eventhandler adding a runtime css class.
I currently don't know why this is happening. Maybe somebody else can jump in here.
By adding an item to the combobox, the control is recreated in js but that isn't a problem I think.
So find another solution: You want a select control in a 'col-sm-6'. That was your reason for the IWBSSelect1.OnHTMLTag I assume.
First I tried the TIWBS4FormGroup. Set the Css property at designtime but this wasn't working. DevTools (yes quite handy!) shows a javascript error. Alexandre??
Looking in the Bootstrap documentation, a form-group is not very special so probably a TIWBS4Region with BSRegionType set to bs4rtFormGroup would be ok.
And it is! With these changes your IWBS4Select example is working.
You can download the example from
https://1drv.ms/u/s!ArMgm0CJ1IAVh0jTer1x...c?e=6OxVKf (too big for the forum because of the included wwwroot resources)
Kind regards,
Jeroen Röttink