For formatting our Dates in the RDL-Files, we use the following format:
=First(FormatDateTime(Fields!SomeDate.Value, 2))
According to this Page, it should take the Computer's Regional Settings.
The problem is: If I call the Reporting-Service via another Service and try to set the Language:
rs.SetExecutionParameters(MapParameters(Report.Parameters).ToArray(), "de-CH");
This gets ignored. I tried to override the Thread-Cultures via
System.Threading.Thread.CurrentThread.CurrentUICulture = new System.Globalization.CultureInfo("de-CH");
System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("de-CH");
Which gets ignored as well. Whats really string: The Reporting-Server itself has de-CH as culture as well, but it keeps using the english date-format.
Can someone tells me what's meant with "Computer's Regional Settings" and why the Reporting-Service refuses to take the passed Culture?
Edit: The language in the Report is
=User!Language
Generally said I'd like to pass the Report-Language from outside, be it via CurrentThread or via Parameter. But both get ignored.
Short Answer
Instead of FormatDateTime, you could use Format and specify your expected output format:
=First(Format(Fields!SomeDate.Value, "dd.MM.yyyy"))
Or another alternative to have the culture in a parameter, but in this case you will have to read the long answer.
Long answer
Your first attempt with the SetExecutionParameters was to set the culture of the parameters, which does not affect the report itself (only the parameters you pass to it).
Your second attempt was to change the culture of the client application, which also does not affect the report (only the client application culture).
The FormatDateTime function usually uses the computer regional settings, but not in Reporting Services. It will take the report culture, which in your case is User!Language.
User!Language returns the language configured in the client web browser when browsing to the report server.
I'm not sure what the behavior is when calling from web services (a specific setting taken or default to en-US).
The Report Language property can be an expression, so nothing stops you from adding another text parameter to the report, say, ReportCulture, and use this in Properties => Language:
=Parameters!ReportCulture.Value
You would have to keep using your expression for the dates:
=First(FormatDateTime(Fields!SomeDate.Value, 2))
You can configure a default value (de-CH in your case), so that this setting will only be specified if you want to override it.