Hello,
Thank you for your inquiry.
According to your description, I used Free Spire.XLS v10.1.4 to convert a newly added sheet to HTML, I got the error “NullReferenceException” when the application executed the “SaveToHtml” method. However, this issue does not exist in the latest commercial version
Spire.XLS Pack(Hotfix) Version:10.9.0.
Sorry to tell you that we only upgrade our free version irregularly, thus, I suggest you test your case with our latest commercial version.
If there are still any questions, please provide your input file as well as you test code for further investigation. You can upload your file here or send it to us (
support@e-iceblue.com) via email.
Sincerely,
Elena
E-iceblue support team