Get Bounds to MultiSelect Markers

            if (canMultiSelect)
            {
                if (Input.GetMouseButtonDown(0))
                {
                    mousePos = Input.mousePosition;
                    double lng, lat;

                    Ray ray = Camera.main.ScreenPointToRay(mousePos);

                    if (Physics.Raycast(ray, out hit))
                    {
                        LayerMask layerMask = hit.transform.gameObject.layer;
                        Transform unitHit = hit.transform;
                        switch (layerMask.value)
                        {
                            case 7:
                                if (!selectedUnits.Contains(hit.transform.GetComponent<Stat>()
                                .marker3D.instance.transform))
                                SelectUnit(unitHit.GetComponent<Stat>().marker3D.instance.transform);
                                break;
                            default:
                                isDragging = true;
                                break;
                        }
                    }
                }

                if (Input.GetMouseButtonUp(0))
                {
                    foreach (OnlineMapsMarker3D child in OnlineMapsMarker3DManager.instance)
                    {
                        var units = child.instance.transform;
                        if (units.gameObject.GetComponent<Stat>() != null)
                        {
                            var pF = units.gameObject.GetComponent<Stat>();

                            if (IsWithinSelectionBounds(units))
                            {
                                if (!selectedUnits.Contains(pF.marker3D.instance.transform))
                                SelectUnit(pF.marker3D.instance.transform);
                            }
                        }
                    }

                    isDragging = false;
                }
            }
            }

        private bool IsWithinSelectionBounds(Transform tf)
        {
            if (!isDragging)
            {
                return false;
            }

            Camera cam = Camera.main;
            Bounds vpBounds = DragGUI.GetVPBounds(cam, mousePos, Input.mousePosition);
            return vpBounds.Contains(cam.WorldToViewportPoint(tf.position));
        }

        public static Bounds GetVPBounds(Camera cam, Vector3 screenPos1, Vector3 screenPos2)
        {
            Vector3 pos1 = cam.ScreenToViewportPoint(screenPos1);
            Vector3 pos2 = cam.ScreenToViewportPoint(screenPos2);

            Vector3 min = Vector3.Min(pos1, pos2);
            Vector3 max = Vector3.Max(pos1, pos2);

            min.z = cam.nearClipPlane;
            max.z = cam.farClipPlane;

            Bounds bounds = new Bounds();
            bounds.SetMinMax(min, max);

            return bounds;  
        }