Adding groups programmatically

Trying to add a group to SharePoint programmatically I’ve found an interesting issue – newly created group was not shown in Groups quick launch, but it was present in the list of all groups. After some time of analyzing SPWeb and SPGroup classes, have found an interesting point. Only groups which are associated with current web are shown in its quick launch. Other site groups are shown in the list of all groups (you can access it by clicking "More…" link in Groups quick launch). So if you want your newly created group to be accessible not only through the list of all groups, but also in Groups quick launch of some webs, you should add it to the collection of associated groups for specific web. This can be done by executing the following:

SPSite site = new SPSite("http://localhost");
SPWeb web = site.OpenWeb();
SPUser user = web.CurrentUser;
web.SiteGroups.Add("MyGroup", user, user, "My description");
SPGroup g = web.SiteGroups["MyGroup"];
web.AssociatedGroups.Add(g);
web.Update();

Don’t forget to call Update for each web, you have modified an associated groups collection to.