Joining two `List` objects into one of abstract data type

Question

Suppose there's the following set up (assume equal lengths and general niceness of the data).

List<String> 
  a = GetStrings(0), 
  b = GetStrings(1);
for(int i = 0; i < a.Count; i++)
  yield return new SuperString{ A = a[i], B = b[i] };

What I wonder is if this can be refactored into a foreach loop and if it'd look very ugly then. I prefer using it before for since the operation will be performed on each of the element pair.

EDIT:

I might have been to scarce on the details. Sorry about that. What if the types are arbitrary? I.e. as the following?

IEnumerable<Cool> a = GetCool();
IEnumerable<Lame> b = GetLame();

for(int i = 0; i < a.Count; i++)
  yield return new Opposites{ A = a[i], B = b[i] };

Answer 1

How about no loop at all?

a.Zip(b, (aa, bb) => new SuperString{A = aa, B = bb})

the benefit of the Zip method is that it will stop at the end of the shorter of the two sequences in the case they're of differing lengths.

Note: if you're using .net < 4, you'll want to take @Cuong's method.

In the case that your types are arbitrary, exactly the same should work:

IEnumerable<Cool> a = GetCool();
IEnumerable<Lame> b = GetLame();
a.Zip(b, (aa, bb) => new Opposites{A = aa, B = bb});

with the caveat that property A of Opposites must be of type Cool and B of type Lame (or a parent type)