linq - Remove objects, and child objects from a list in C# where they match an object property in another list -

i need c# linq query remove objects in list based on whether match property in list. in addition, objects can contain children of same type , need remove them if there not match.

in example, want remove children of children. match doesn't need hierarchical - basic match. here classes , failed attempt. awesome!

public class gsdmegamenu     {         public int id { get; set; }          public int portalid { get; set; }            public int tabid { get; set; }       }   public class menuitem     {         public int id { get; set; }          public int portalid { get; set; }            public int tabid { get; set; }         public list<menuitem> children { get; set; }      }   list<gsdmegamenu> megamenuitems = gsdmegamenu.getallgsdmegamenus(); rootnode.children.removeall(x => !megamenuitems.any(y => y.tabid == x.tabid)); 

if need process children of children have explicitly loop though them. removeall not linq method it's method on list class. need call on every children list.

rootnode.children.removeall(x => megamenuitems.all(y => y.tabid != x.tabid)); foreach (menuitem node in rootnode.children) {     if (node.children != null)     {         node.children.removeall(x => megamenuitems.all(y => y.tabid != x.tabid));     }  } 

update

if after purely linq solution has read-only, can't manipulate existing lists, can create new ones. not recommend in case though. in case loop above seems more fitting.

rootnode = rootnode.children.where(x => megamenuitems.select(y => y.tabid).contains(x.tabid))     .select(z => new menuitem     {         id = z.id, portalid = z.portalid, tabid = z.tabid,          children = z.children == null ? null              : z.children.where(x => megamenuitems.select(y => y.tabid).contains(x.tabid)).tolist()            })     .tolist(); 

for efficiency (not matter in case), rewrite this:

func<menuitem, bool> predicate = x => megamenuitems.select(y => y.tabid).contains(x.tabid); rootnode = rootnode.children.where(predicate)     .select(z => new menuitem     {         id = z.id, portalid = z.portalid, tabid = z.tabid,          children = z.children == null ? null             : z.children.where(predicate).tolist()     })     .tolist();