Prompts to Discard digital signature while saving

[Jaydeep]

Greetings,

I have Excel Template File developed using VSTO project option in Visual
Studio. This file doesn't have any macros but we have digitally signed this
excel sheet. Using this template we are exporting excel sheet. Once exported
if user tries to save the file excel is prompting that "You have modified a
signed project. .... Discard signature and save?"

I suspect there can be something in VSTO code that would cause modification
of signed project. but I don't have a single line of code as macro. Still
don't know why its promting this message.

Can someone tell me which action can cause change in signed project?

Thanks in advance
Jaydeep