Linq JOIN on internal collection

Question

0.00/5 (No votes)

See more:

Hello,

I got the following collection:

C#

List<(string, List<string>)> items = new List<(string, List<string>)>
{
    ("col1", new List<string>{"1","2","3"}),
    ("col2", new List<string>{"1","3","4"})
};

I need to transform it into List<string, (bool, bool)>:

C#

{
    ("1", (true, true)),  // (because "1" exists in col2)
    ("2", (true, false)), // (because "2" does NOT exists in col2)
    ("3", (true, true)),
    ("4", (false, true))
}

Could you please advise how to accomplish this in a nice fashion? JOIN statement would be sufficient?

Thank you in advance

What I have tried:

I tried using GroupBy, but its very cumbersome

Posted 5-May-20 7:57am

Yoyosch

Updated 5-May-20 22:17pm

Richard Deeming

v2

Add a Solution

3 solutions

Solution 3

Try this:

C#

List<(string, List<string>)> items = new List<(string, List<string>)>
{
    ("col1", new List<string>{"1","2","3"}),
    ("col2", new List<string>{"1","3","4"})
};

var result = items
	.SelectMany(x=>x.Item2.Select(y=> Tuple.Create(y, x.Item1)))
	.GroupBy(x=>x.Item1)
	.Select(grp=> new {Item1 = grp.Key, Item2 = items.Select(x=>grp.Any(y=>y.Item2==x.Item1)).ToList()})
	.ToList();

Result:

1, {true, true}
2, {true, false}
3, {true, true} 
4, {false, true}

Posted 5-May-20 22:18pm

Maciej Los

Comments

TheRealSteveJudge 6-May-20 4:43am

5*

Maciej Los 6-May-20 6:00am

Thank you!

Solution 1

I got the following solution:

List<(string, List<string>)> items = new List<(string, List<string>)>
{
("col1", new List<string>{"1","2","3"}),
("col2", new List<string>{"1","3","4","5"})
};

var distinctIds = items.SelectMany(x => x.Item2).Distinct();

var ids = distinctIds.Select(x => (x, items.First(y => y.Item1 == "col1").Item2.Any(y => y == x), items.First(y => y.Item1 == "col2").Item2.Any(y => y == x))).ToList();

It works, but is it possible to embed this logic into one linq query?

Posted 5-May-20 8:12am

Yoyosch

Comments

Maciej Los 6-May-20 4:19am

Yes, it is possible. See solution #3 ;)

BTW: your answer is NOT a solution. I'd suggest to delete it to avoid down-voting. Such of content should be posted as a comment or you have to improve your question.

Add a Solution

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard Deeming · Accepted Answer · 2020-05-05T08:20:00

Doing this as a single statement won't be particularly clean, but it can be done:

C#

var result = items.Where(i => i.Item1 == "col1").SelectMany(i => i.Item2)
    .Union(items.Where(i => i.Item1 == "col2").SelectMany(i => i.Item2))
    .Select(key => 
    (
        key, 
        (
            items.Any(i => i.Item1 == "col1" && i.Item2.Contains(key)), 
            items.Any(i => i.Item1 == "col2" && i.Item2.Contains(key))
        )
    ))
    .ToList();

Enumerable.Union Method (System.Linq) | Microsoft Docs[^]

Linq JOIN on internal collection

3 solutions

Solution 2

Solution 3

Solution 1

Add your solution here

Preview 0

Linq JOIN on internal collection

3 solutions

Solution 2

Solution 3

Solution 1

Add your solution here

Preview 0

Existing Members

...or Join us