We have a system that runs in IIS.
The system should always run using the same \"culture\", but we cannot rely on the server settings being set correct.
One
Do you dynamically change the culture? If not, you can set the culture in the web.config file.
You can also set it at page level:
<%@Page Culture="fr-FR" Language="C#" %>
And on the thread:
Thread.CurrentThread.CurrentCulture = new CultureInfo("de-DE");
But for what you are using, the page-level or web.config level seems like the most appropriate perhaps.