Hi,
The LoadDocumentFromFile method analyzes the provided file name and load a library or a drawing document, depending on the file extension, while the LoadDrawingFromFile and LoadLibraryFromFile methods expect and load a drawing document and a library document respectively. So if you know whether you are loading a drawing document or a library document, it is better to use the corresponding method. In this way there won't be any unecessary checks and you won't have to cast the read document to a drawing or a library document later on.