I've been looking through the TDataset class and its string fields, in Delphi XE2 and noticed that AsWideString returns a type of UnicodeString. However it gets the value from the function TField.AsString: String which in turn calls TFIeld.AsAnsiString:AnsiString. Therefore any unicode characters would be lost? Also the buffer which is passed to TDataset.GetFieldData is declared as an array of AnsiChar.
Am I understanding this correctly?
No, you should be examining the TWideStringField class which is for Unicode fields and the TStringField class which is for non-Unicode strings. TField is just a base class and TField.GetAsWideString is a virtual method with a fall back implementation that is overridden by descendants that are Unicode aware.