c# - EF LINQ - Return entities that contain an entire collection -

i trying troubleshoot following linq query:

public jsonresult searchnodesbytags(string[] tags) {          var nodes = _dbcontext.nodes.             where(n => n.tags.all(t => tags.contains(t.displayname)))             .select(n => new {n.nodenativeid, n.nodename, n.nodeclass.classname})             .tolist();      return json(nodes); } 

the query returning single node not associated tag. want do, return nodes have tags.

  .where(n => n.tags.all(t => tags.contains(t.displayname))) 

the way constructed, you're going end nodes every tag in node.tags has name in tags whitelist, includes nodes no tags.

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you might want use answer here on subsets:

_dbcontext.nodes     .where(n => !tags.except(n.tags.select(t => t.displayname)).any())      .select(... 

• set1.except(set2) contains elements of set1 aren't in set2
• !set1.except(set2).any() == true if set2 includes every element of set1

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edit

it pointed out in comments using except generate problematic queries, thinking option superset database, , further filter objects within application:

_dbcontext.nodes     // filter nodes of input tags     .where(n => n.tags.any(t => tags.contains(t.displayname)))      // select information required     .select(n => new {         n.nodenativeid,          n.nodename,          classname = n.nodeclass.classname,         tagnames = n.tags.select(t => t.displayname) })      // materialize super set database     .tolist()      // filter nodes tags remain     .where(n => !tags.except(n.tagnames).any())      // produce result in anonymous class     .select(n => new { n.nodenativeid, n.nodename, n.classname })     .tolist(); 

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edit 2

i saw 1 here might work you, requires tag.displayname unique, since fail if have multiple tags same displayname:

_dbcontext.nodes      .where(n => n.tags.count(t => tags.contains(t.displayname)) == tags.count)      .select(...