Redmine

Hi,
I use Redmine server on IIS 6.2 on localhost in Windows 8.1.

Environment:
  Redmine version                2.3.4.stable
  Ruby version                   1.9.3-p448 (2013-06-27) [i386-mingw32]
  Rails version                  3.2.13
  Environment                    development
  Database adapter               SQLite
Redmine plugins:
  no plugin installed

I work on my C# application. All my GetObjectList, GetObject and CreateObject methods work just fine, but while using DeleteObject and UpdateObject nothing happens. No exception is thrown, everything seems to be okey, but on Redmine no changes are made. Does anyone could help me with that problem, please?
I use those methods in this way:

Trying to delete user with id = 4:

manager.DeleteObject<User>("4", null);

Trying to change user's email:

User us = manager.GetObject<User>("4", null);
us.Email = "new@email.com";
manager.UpdateObject<User>("4", us);

Do you have any ideas what could be a possible reason for that problem?
Thank you!