How to remove a user from a sharepoint group by programe

You can remove a user by its LoginName of by its internal UserId from a specified group.

Here is an example of both

Remove by UserId -

Method 1 –

web.AllowUnsafeUpdates = true;

SPGroupCollection collGroups = web.SiteGroups;

SPUserCollection usercoll = siteobj.RootWeb.SiteUsers;

int ID = oWeb.Users[UserName].ID;

usercoll.RemoveByID(ID);

web.Update();

web.AllowUnsafeUpdates = false;

Method 2 –

web.AllowUnsafeUpdates = true;

SPGroupCollection collGroups = web.SiteGroups;

SPUserCollection usercoll = siteobj.RootWeb.SiteUsers;

String LoginID = web.CurrentUser.LoginName;

usercoll.Remove(LoginID);

web.Update();

web.AllowUnsafeUpdates = false;