Question

for example, the following composite query + method looks not good enough. I am seeking for better approach.

        foreach (var x in A)
        {
            foreach (var y in B)
            {

                if (getLazyList(x, y).Any(z => z == y))
                {
                    blacklist.Add(x);
                    break;
                }

            }
        }

Now compared to this one provided by: @Bob Vale

 var q = from x in A 
         from y in B
         where getLazyList(x,y).Contains(y)
         select x;
 blacklist.AddRange(q);

would 2nd method do the unnecessary loops? in 1st example i use .any() and break to escape the inner loop, how would linq handle this in 2nd case?

Answer 1

how about this;

var q = from x in A 
        from y in B
        where getLazyList(x,y).Contains(y)
        select x;
blacklist.AddRange(q);

if AddRange doesn’t work then just replace the last line with

foreach (var x in q) blacklist.Add(x);

To handle the break you’d have to use an any clause

var q = from x in A
       where B.Any(y=>getLazyList(x,y).Contains(y))
       select x