Error when calling new to create an instance of my .net dll in Axapta

Hi, I wrote a .net dll (c#) which handles some special document up and downloads to sharepoint from AX. I added the dll to the GAC, referenced it in AX and now I try to create a class in AX to use the dll-functions. The declaration in the AX-class works fine:

class WS_SharepointUpload {   WSDAXSharepointDocuments.DAXSharepointDocuHandler mossDocuHandler; ....

but when I like to instantiate the dll in my function to upload:

str uploadDocument(str _url, str _site, str _library, str _file, str _axid, str _axcompany, str _axrecid, str _axreference) {   mossDocuHandler = new WSDAXSharepointDocuments.DAXSharepointDocuHandler;

I got an error which says s.th like "Class WSDAXSharepointDocuments.DAXSharepointDocuHandler does not contain this function.

What am I doing wrong???