CODEWITHSUNDEEP
vb.netlistlinq
DVELPR
DVELPR

Reputation: 304

Linq How to combine List Items to other List items

I have multiple list of string with some items

want to combine every items together like below

        Dim _rsltitm = Nothing
        For Each _itm1 In _lst1
            For Each _itm2 In _lst2
                For Each _itm3 In _lst3
                    _rsltitm &= vbNewLine & _itm1 + _itm2 + _itm3
                Next
            Next
        Next

above code is working fine but i have more than 8 lists or sometimes 11

so i need linq to combine multiple list of string items together

i am trying like this but i could not

    Dim _rslt = From itm In _lst1 Select (Function(x) From itm2 In _lst2 Select (Function(d) x & d))

Upvotes: 1

Views: 145

Answers (1)

jmcilhinney
jmcilhinney

Reputation: 54417

I just tested this code and it seems to do what you want:

Dim list1 As New List(Of String) From {"1", "2", "3"}
Dim list2 As New List(Of String) From {"A", "B", "C"}
Dim list3 As New List(Of String) From {"7", "8", "9"}
Dim list4 As New List(Of String) From {"X", "Y", "Z"}

Dim lists = {list1, list2, list3, list4}

Dim result = lists.Aggregate(Function(current, list)
                                 Dim combinedList As New List(Of String)

                                 For Each prefix In current
                                     combinedList.AddRange(From suffix In list Select prefix & suffix)
                                 Next

                                 Return combinedList
                             End Function)

You just add all your lists to that lists array and result should end up containing the desired result.

I feel like that Lambda body should be able to be LINQified a bit more but my initial attempts didn't work so I gave up quickly. If you want to put some more time into it, you're welcome to.

EDIT:

Here's that in a function:

Private Function CombineLists(ParamArray lists As List(Of String)()) As List(Of String)
    Return lists.Aggregate(Function(current, list)
                               Dim combinedList As New List(Of String)

                               For Each prefix In current
                                   combinedList.AddRange(From suffix In list Select prefix & suffix)
                               Next

                               Return combinedList
                           End Function)
End Function

In my example, I could either call that like so:

Dim result = CombineLists(list1, list2, list3, list4)

or like so:

Dim lists = {list1, list2, list3, list4}

Dim result = CombineLists(lists)

Upvotes: 2

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