Recently I began seeing corrupted excel files coming from a production grid exports. When attempting to open the file you are greeted with everyone's favorite error:
"Excel found unreadable content in '<filename>.xlsx'. Do you want to recover the contents of this workbook? If you trust the source of this workbook, click Yes."
Looking futher into the error after attempting recovery, it appears that an illegal character is being written to the sharedStrings.xml file:
<si><t>�</t></si>
I've yet to track down where exactly this comes from but it occurs both in the very latest SR of 11.1 as well as an older release of 10.3. Regardless of the source of this character, it seems reasonable to expect the ExcelExporter to not write illegal XML.
Can you post a small sample that reproduces the issue? I wasn't able to get anything like this written out in a file.
Create a property on your data object that is a char and assign it the null character '\0'.
I have attached a quick project to demonstrate the issue.