StackOverflowException getting all building blocks

Hi, I need to get all building blocks in a certain distance with this code:

(Taken from BuildingGrades)

Code:

            List<BuildingBlock> Blocks = new List<BuildingBlock>();
            Blocks.Add(StartBlock);            Action<BuildingBlock> queue_attached_blocks = null;
            queue_attached_blocks = (Block) =>
            {
                foreach(var collider in UnityEngine.Physics.OverlapSphere(Block.transform.position, 3.5f))
                {
                    var next_block = collider.GetComponentInParent<BuildingBlock>();
                    if(next_block == null || Blocks.Contains(next_block)) continue;
                    queue_attached_blocks(next_block);
                }
            };
            queue_attached_blocks(StartBlock);

It works fine for small and medium sized bases.

But as soon as I try to loop through a very large base, i get a StackOverflowException.

Is it possible to increase the stack size somehow?
Or would anyone be able to help me to optimize this snippet?

 

Ah i pasted the wrong snippet, the other one is using !Blocks.Add(next_block)) continue; (HashMap)