Aug 06, 2019 06:07 AM|Yongqing Yu|LINK
Do you think it might be a cache problem?
No, that's not the reason.
According to your description, I guess the question should still be on the imageUrl of the pictures.
Can you be sure that the urls of these pictures are correct?
I recommend that you use F10 to step by step debug the code behind and check the imageUrl for the current image in the OnSelectedIndexChanged event.
Or you can use F12, when you switch to click listbox, monitor the status of the image in the Network tab and whether the status code is green, you can refer following gif :
If these still not solve your issue, please provide your complete codes for us to test (with your imageurl details).