Thanks for your reply.
hi and thank you for reply. i solve this error.
but i have another problem. in PermissionAppService i want to load only parent permissions with childrens of this parents.
and i write this code:
var permissions = _permissionManager.GetAllPermissions(true).Where(a=>a.Parent==null).ToList();
when i write this where condition, only parent permissions returned, but childrens of parent permissions are null and does not load. and when i remove where condition,all parents and childerens are load together and my program display incorrect tree. how can i solve this problem?