c# - Get the client Task Folder (Outlook)

Question

I'm currently on an application which permits you to open a Outlook task.

For getting the folder I use :

ApplicationClass _app;
NameSpace _nameSpace;
MAPIFolder folder;

app = new ApplicationClass();
nameSpace = app.GetNamespace("MAPI");
folder = nameSpace.GetDefaultFolder(OlDefaultFolders.olFolderTasks);

It works in the server side, but when I use the application from a client, it doesn't work.

How can I access to the client Outlook folder?

PS : It's for Exchange Accounts