Translate:

collection.Where(x => x.F[n] == c)

to:

{ $match : { "F.n" : c } }

where `x.F` is of type `List<T>` and `x.F[n]` is represented as a MethodCallExpression using the special method name `get_Item` and `n` is a constant integer and `c` is a constant of type `T`.