Find and count from array in another array using linq C#

Question

I have the following scenario:

I get a collection of records from a data source and add them to a List

List<Entity> e = new List<Entity>();
foreach (var elm in datasource)
{
      e.Add(new Entity { First = elm.First, Second = elm.Second, Third = elm.Third });
}

This gives me something like:

// -> First = John, Second = Sally, Third = Ingrid
// -> First = Sally, Second = Ingrid, Third = James
// -> First = Ingrid, Second = Sally, Third = James

I have an array of possible values that can be true and possible values that can be negative, in a List

List<string> positives = { "John", "Sally" }
List<string> negatives = { "Ingrid", "James" }

I am looking for an elegant why of matching the amount of positives and the amount of negatives I have in the generic list e, as per the above? Would something like this be possible with LINQ?

As I am not familiar with LINQ have no idea where to start. I tried something like:

var pos = e.SelectMany(s => s in positives).Count()

But this throws an exception.

Any help would be greatly appreciated

Saeed Neamati · Accepted Answer · 2013-11-15 10:01:32Z

3

SQL's in clause in LINQ is Contains method.

Test:

var pos = e.SelectMany(s => positives.Contains(s)).Count();

Seems that I haven't understood your question. Reading again.

To be honest, your question in not well-phrased.
But based on what I understood, I think the correct response is:

var pos = e.SelectMany(i => positives.Contains(i.First) 
                            || positives.Contains(i.Second) 
                            || positives.Contains(i.Third)).Count();

edited Nov 15, 2013 at 10:01

answered Nov 15, 2013 at 9:55

Saeed Neamati

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Comments

David Pilkington · Accepted Answer · 2013-11-15 09:57:27Z

1

You are using in incorrectly

e.SelectMany(s => positives.Contains(s)).Count();

but what I assue you are wanting is this

var pos = e.Count(s => positives.Contains(s.First) || positives.Contains(s.Second) ||positives.Contains(s.Third));

var neg= e.Count(s => negatives.Contains(s.First) || negatives.Contains(s.Second) ||negatives.Contains(s.Third));

answered Nov 15, 2013 at 9:57

David Pilkington

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Gregoire · Accepted Answer · 2013-11-15 10:06:54Z

0

or you can use an any

var pos = e.SelectMany(i => 
    positives.Any(p=> p==i.First || p==i.Second || p==i.Third))
    .Count();

answered Nov 15, 2013 at 10:06

Gregoire

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