TWebUpdate LanguageIDs list and more....

I can not find the LanguageIDs list in the component documentation, where can I find it?

Another point, the method "GetWhatsNew ()" has returnd me always NULL when it should return a StringLits with the contents of the file "WhatsNew.txt", this method does not work ???

The LanguageID property can be used have multiple language dependent what's new file references in your update control .INF file.

Default, there is only one what's new referenced in the .INF file.
file=location of file 

In case you want to provide 3 different what's new files in 4 languages , you could put in your update control file:

file=location of file in english

file=location of file in french

file=location of file in german

When you set WebUpdate.LanguageID = 'GER', it would then fetch the german version of the file.

To get the default what's new file, make sure to set WebUpdate.LanguageID = ''.