Carrotware.CMS.Core.ExtendedUserData.RemoveFromSite C# (CSharp) Method

        public bool RemoveFromSite(Guid siteID)
        {
            using (CarrotCMSDataContext _db = CarrotCMSDataContext.Create()) {
                carrot_UserSiteMapping map = (from m in _db.carrot_UserSiteMappings
                                              where m.UserId == this.UserId
                                                && m.SiteID == siteID
                                              select m).FirstOrDefault();

                if (map != null) {
                    _siteIDs = null;

                    _db.carrot_UserSiteMappings.DeleteOnSubmit(map);
                    _db.SubmitChanges();

                    return true;
                } else {
                    return false;
                }
            }
        }

		protected void btnRemove_Click(object sender, EventArgs e) {
			CheckBox chkSelected = null;
			HiddenField hdnUserId = null;

			foreach (GridViewRow dgItem in gvUsers.Rows) {
				hdnUserId = (HiddenField)dgItem.FindControl("hdnUserId");

				if (hdnUserId != null) {
					chkSelected = (CheckBox)dgItem.FindControl("chkSelected");

					Guid guidUsrID = new Guid(hdnUserId.Value);
					ExtendedUserData exUsr = new ExtendedUserData(guidUsrID);

					if (chkSelected.Checked) {
						exUsr.RemoveFromSite(guidSiteID);
					}
				}
			}

			Response.Redirect(SiteData.CurrentScriptName + "?id=" + guidSiteID.ToString());
		}