vb.net For Each loop

Question

I would like to loop through two lists using a For each loop.

dim data as list(of pointpairlist)
For each recLine in records
    For Each chan In recLine.channels and d in data
      d.add( func(chan) )
    Next
next

note: each record line has one sample from each channel recorded. ie each record line is a slice of a 32 sensor recordings. I want to build up a x,y list of data points for each channel (the x axis is common to all channels)

Is there some way to do it similar to what i have above (avoiding indexing variables)

Answer 1

The best way to iterate over two different collections in a single loop is to use indexers.

For index As Integer = 0 To recLine.channels.Count - 1
    data(index) = func(chan(index))
Next

As @0xA3 comments, you can also a while loop, calling GetEnumerator, MoveNext and Current directly on each collection, but this buys you nothing.

I realize you want to avoid using indexers, but there is no simple language support for anything else.

This is the case also for C#.

Why do you need to avoid indexers?

Answer 2

Nest the loops. I cannot reverse-engineer the actual declarations from the snippet, but something like this:

    Dim data As List(Of PointPairList)
    ''...
    For Each point In data
        For Each chan In point.recLine
            func(chan)
        Next
    Next