Question

I have referred to the following question at: Using foreach loop to iterate through two lists. My question is this, with regards to the chosen answer: Can the o.DoSomething be a comparison? As in:

For Each a in ListA.Concat(ListB)
    If(a from ListA=a from ListB) Then
        Do Something here
    End If
Next

As you might’ve guessed, I’m using VB.Net and would like to know how I can do what I have shown here. That would basically be to iterate through a joined list separately/independently. Thanks!

Answer 1

Your question indicates that you need a Join operation, because it’s not that you want to iterate over two lists, but you also want to match like items from one list to the other.

    Dim joinedLists = From item1 In list1 _
                    Join item2 In list2 _
                    On item1.Bar Equals item2.Bar _
                    Select New With {item1, item2}

    For Each pair In joinedLists
        'Do work on combined item here'
        'pair.item1'
        'pair.item2'
    Next

Other answers recommend Zip. That is simply a function that takes two sequences and produces a single result, much like join, but it is geared to work in a FIFO method over both lists. If you need connections made based on an equality, Join is the specifically built to be right tool for this job.