Find intersect of different dictionary values variable

Question

I have one Dictionary declared as type

var dictionary1 = Dictionary<string, Type1>

and another as

var dictionary2 = Dictionary<string, Type2>

Each dictionary value type has a public variable called classid so:

dictionary1["key"].classid = 100

is also in:

dictionary2["key"].classid = 100

I know they are of different types, but is there an inbuilt way to find the intersections of just these two private variables and possibly return me a dictionary of that single type? So if the classid were equivalent I could get an intersected dictionary of Type Dictionary1?

Why is `classid` private if you need to use it outside the class? — Ben Aaronson, May 15 '14 at 08:51
Wait, If `classid` is private `dictionary1["key"].classid = 100;` won't compile. — Sriram Sakthivel, May 15 '14 at 08:52
So you want all elements of `dictionary1` where the `classid` of the value is also found in the values of `dictionary2`? To the keys have to match? Not exactly clear IMHO. Maybe you should give some example input/output. — sloth, May 15 '14 at 08:59

Avner Shahar-Kashtan · Accepted Answer · 2014-05-15T08:59:50.873

1

This isn't the most elegant query, but it should do the trick:

var intersection = dictionary1
.Where(kvp1 => 
   dictionary2.ContainsKey(kvp1.Key) 
   && dictionary2[kvp1.Key].classid = kvp1.Value.classid)
.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

This should fetch all key-value pairs in dictionary1 whose keys also exist in dictionary2, and whose classid matches the dictionary2 object's classid. Those key-value pairs are then transformed into a new dictionary.

edited May 15 '14 at 08:59

answered May 15 '14 at 08:54

Avner Shahar-Kashtan

14,492
3
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@user2281557 Glad to hear. If this has helped you, don't forget to mark the answer as Accepted using the checkmark-icon to the left. – Avner Shahar-Kashtan May 15 '14 at 09:16
You could also use `TryGetValue` rather than `ContainsKey(key)` followed by a `dictionary[key]` lookup: one lookup per iteration should be quicker than two. – LukeH May 15 '14 at 09:19
@LukeH That's true, but until C# 6 comes around with the ability to declare variables as part of an `out` method call, this would require breaking the lambda expression into a full-scale {}-covered block scope, which is ugly. – Avner Shahar-Kashtan May 15 '14 at 09:24

score 1 · Answer 2 · edited May 23 '17 at 12:31

As an alternative to Where/ContainsKey, you could also use a simple join, which is more readable and (probably) faster for larger sets of data:

var result = from kv1 in dictionary1
             join kv2 in dictionary2 on 
                new {kv1.Key, kv1.Value.classid} equals 
                new {kv2.Key, kv2.Value.classid}
             select kv1;

var new_dict = result.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

score 0 · Answer 3 · answered May 15 '14 at 08:55

you can use below mentioned code

        Dictionary<int, string> t = new Dictionary<int, string>();
        Dictionary<int, string> t1 = new Dictionary<int, string>();
        t.Add(100, "f");
        t1.Add(100, "f2");

        var abc=t.Where(p=>t1.Any(q=>q.Key==p.Key));

score 0 · Answer 4 · edited May 23 '17 at 11:59

0

Yes but dictionaries may not be what you want and this question may be a duplicate phrased differently:

C# Linq intersect/except with one part of object

BTW the property you want to use for the intersection should be public.

edited May 23 '17 at 11:59

Community

1
1

answered May 15 '14 at 09:00

Murphy

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Find intersect of different dictionary values variable

4 Answers4