Question

What is equivalent of following code snippet in lambda expression?

int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };

var pairs =
    from a in numbersA
    from b in numbersB
    where a < b
    select new { a, b };

Answer 1

Here is a LINQ expression using method syntax (as opposed to query syntax):

int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 }; 
int[] numbersB = { 1, 3, 5, 7, 8 }; 

pairs = numbersA
  .SelectMany(_ => numbersB, (a, b) => new { a, b })
  .Where(x => x.a < x.b);

The original query is translated into this:

int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 }; 
int[] numbersB = { 1, 3, 5, 7, 8 }; 

pairs = numbersA
  .SelectMany(_ => numbersB, (a, b) => new { a, b })
  .Where(x => x.a < x.b)
  .Select(x => new { x.a, x.b });

However the last Select isn’t required and can be removed.