Multiple instructions with linq select

Question

I have two objects: A containing a list of B objects :

• A has a property BList which is a list a B objects
• B has a property A

I call a method which returns a list of B elements. Then I want to group these B elements by their A property and in the end get a list of A objects :

var groupedByA = bList.GroupBy(b => b.A).Select(a => a.Key).ToList()

That works fine, but in my case, the BList of these A objects are not set, so I also want to associate the B list of the groupBy instruction to A, something like

var groupedByA = bList.GroupBy(b => b.A).Select(a => a.Key then a.Key.BList = a.Val).ToList()

Any idea how can I do that?

Answer 1

You could write an statement lambda:

.Select(group => {
  var bList = group.ToList();
  var a = group.Key;
  a.BList = bList;
  return a;
})

You may want to add some comments or otherwise note that the objects will be modified. Normally you would expect LINQ statements to be side-effect free.