Set permissions the 'Right-way' at SPListItem & SPWeb

    There has always been a confusion between assigning custom permissions between a listitem and        a sharepoint site.

    Setting site level permissions programmatically at website level

    Code :

            SPSecurity.RunWithElevatedPrivileges(delegate()

            {

                using (SPSite site = new SPSite("http://site/subsite"))

                {

                    using (SPWeb webSubSite = site.OpenWeb())

                    {

                        webSubSite.BreakRoleInheritance(false);

                        SPGroup group = webSubSite.Site.RootWeb.SiteGroups["Group_Display_Name"];

                        SPRoleDefinitionCollection SubSiteWebRoleDefn = webSubSite.RoleDefinitions;

                        SPRoleAssignment objRoleAssign = new SPRoleAssignment((SPPrincipal)group);

                        objRoleAssign.RoleDefinitionBindings.Add(SubSiteWebRoleDefn["Read"]);

                        webSubSite.RoleAssignments.Add(objRoleAssign);

                        webSubSite.Update();

                    }

                }

            });


    Setting site level permissions programmatically at listitem level
    
    Code :

            SPSecurity.RunWithElevatedPrivileges(delegate()

            {

                using (SPSite site = new SPSite(currentItem.Web.Site.ID))

                {

                    using (SPWeb web = site.OpenWeb(currentItem.Web.ID))

                    {

                        web.AllowUnsafeUpdates = true;

                        SPList elevatedmyList = web.Lists[properties.ListId];

                        elevatedItem.BreakRoleInheritance(false);

                        elevatedItem.RemoveAllItemPermissions();

                        SPGroup AGOIntranetUsersGroup = elevatedItem.Web.SiteGroups["Group_Display_Name"];

                        SPRoleDefinition AGOIntranetUsersGroupRole = elevatedItem.Web.RoleDefinitions["Read"];

                        elevatedItem.SetPermissions(AGOIntranetUsersGroup, AGOIntranetUsersGroupRole);

                        elevatedItem.SystemUpdate();

                        web.AllowUnsafeUpdates = false;

                    }

                }

            });