Is there any way to prevent the excel exports from getting the warning "The file you are trying to open 'report_grid.xls' is in a different format than specified by the file extension"
It's a common issue with new version of ms excel, but i am unable to generate this issue.
http://forums.asp.net/t/1221467.aspx?Export+GridView+to+Excel+xlsx+Excel+2007+Format+
After some research, i found this lib which (by comments) is capable to remove this warning.
http://phpexcel.codeplex.com/wikipage?title=Examples&referringTitle=Home
Can you please check it's demos, if it is working fine or not. After that, i can incorporate it in grid code lib.
This can be solved with a registry edit (or a group policy).
Change the version to your Excel Version appropriately (Office 2003 = 11.0, Office 2007 = 12.0, Office 2010 = 14.0 and Office 2013 = 15.0).
[HKEY_CURRENT_USERSoftwareMicrosoftOffice<version#>ExcelSecurity]
"ExtensionHardening"=dword:00000000