public static void SetFolderPermissions(SPFolder folder,SPFieldUserValue target)
        {

            if (!folder.Item.HasUniqueRoleAssignments)
            {
                folder.Item.BreakRoleInheritance(false);
                folder.Item.Update();
            }

            //permiso de lectura al usuario
            SPRoleDefinition role = folder.ParentWeb.RoleDefinitions.GetByType(SPRoleType.Reader);
            SPRoleAssignment roleAssignment;
            SPUser oneUser = target.User;
            roleAssignment = new SPRoleAssignment(oneUser);
            roleAssignment.RoleDefinitionBindings.Add(role);
            folder.Item.RoleAssignments.Add(roleAssignment);

            //permiso de edición al grupo de control
            int principalID = Document.getControlGroup(folder.ParentWeb).LookupId;
            SPPrincipal principal = folder.ParentWeb.SiteGroups.Cast<SPPrincipal>().SingleOrDefault(g => g.ID == principalID);

            SPRoleAssignment groupRoleAssigment = new SPRoleAssignment(principal);
            SPRoleDefinition groupRoleDefinition = folder.ParentWeb.RoleDefinitions.GetByType(SPRoleType.Editor);
            groupRoleAssigment.RoleDefinitionBindings.Add(groupRoleDefinition);
            folder.Item.RoleAssignments.Add(groupRoleAssigment);

            //folder update
            folder.Update();

            //web update
            folder.ParentWeb.Update();


        }