For each in double list - vb.net

Question

Is it possible to do a for each joining two list and browse through the new "duo list" ?
something like :
For Each elm In list1 Join list2
elm.obj1 // objet with list1 type
elm.obj2 // object with list2 type
next elm
Lists have the same length.

Answer 1

You can join by index with LINQ's Enumerable.Zip and create an anonymous type:
Dim zipped = list1.Zip(list2, Function(obj1, obj2) New With {Key obj1, Key obj2})
For Each pair In zipped
Console.WriteLine(pair.obj1)
Console.WriteLine(pair.obj2)
Next
Note that zipped is not a collection yet but a query. Whenever you will enumerate it(f.e. with For Each, First, ToList etc.) you will execute this query again. If you need to persist it you can create a list or array(ToList/ToArray) and access this instead.
The lazy evaluation of many LINQ methods is called Deferred Execution.

Answer 2

If you mean that you want to enumerate a single, combined list then you would do this:
For Each item In list1.Concat(list2)
'Use item here.
Next
If what you actually mean is that you want to access the items in both lists at the same index at the same time then how would a For Each loop make sense? In that case you'd use a For loop and get both items by index:
For i = 0 To list1.Count - 1
Dim item1 = list1(i)
Dim item2 = list2(i)
'Use item1 and item2 here.
Next
Taking into account the Zip method used in the other answer and combining it with my Tuple suggestion:
For Each tpl In list1.Zip(list2, Function(a, b) AddressOf Tuple.Create)
Console.WriteLine(tpl.Item1)
Console.WriteLine(tpl.Item2)
Next