CODEWITHSUNDEEP
c#.netvb.netlinq
John Bustos
John Bustos

Reputation: 19544

Return items in one list based upon their matching index in another using Linq

I know I could very easily accomplish this using loops, but I'm looking for the most efficient solution for my question.

Suppose I have 2 lists(of string):

Dim lst1 as new list(of string)
Dim lst2 as new list(of string)

And both have the same number of elements, for example:

Lst1:    Lst2:
a        abc1
a        abc2
b        abc3
a        abc4
b        abc5
c        abc6
a        abc7
c        abc8

Now, I'm looking to get, for example, all the elements from lst2 for which the corresponding elements in Lst1 = "a"

So my final result will be:

Lst3 = Items from Lst2 where corresponding Items in Lst1 = "a"
Lst3 = {abc1, abc2, abc4, abc7}

Again, I know this would be SUPER easy to do with loops, but I'm wondering how to do this via Linq.

Thanks!!!

Upvotes: 0

Views: 1197

Answers (3)

Kundan Singh Chouhan
Kundan Singh Chouhan

Reputation: 14282

In a more generic way you could try some thing like this :

C#

List<String> lst3 = lst2.Where((item, index) => 
                               item.StartsWith(lst1.Distinct()[index])).ToList();

VB

Dim lst3 As List(Of [String]) = lst2.Where(Function(item, index)
                                item.StartsWith(lst1.Distinct()(index))).ToList()

Hope this will help !!

Upvotes: 0

L.B
L.B

Reputation: 116098

List<string> Lst1 = new List<string> { "a", "a", "b", "a", "b", "c", "a", "c"};
List<string> Lst2 = new List<string> { "abc1", "abc2", "abc3", "abc4", "abc5", "abc6", "abc7", "abc8" };

var Lst3 = Lst2.Where((s, i) => Lst1[i] == "a").ToList();

Upvotes: 2

Rohit Vats
Rohit Vats

Reputation: 81233

Try this -

List<String> Lst3 = Lst2.Where((item, index) =>
                              Lst1[index].Equals("a")).ToList();

Upvotes: 1

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