# Creating a list from two lists with all possible combinations of elements

**URL:** <https://forum.dynamobim.com/t/creating-a-list-from-two-lists-with-all-possible-combinations-of-elements/11082>\
**Category:** Lists-Logic\
**Created:** [April 16, 2017, 12:26pm UTC](https://forum.dynamobim.com/t/creating-a-list-from-two-lists-with-all-possible-combinations-of-elements/11082 "2017-04-16T12:26:06Z")\
**Posts on this page:** 1\
**Showing post:** 4

<div class="post-metadata">

**Author:** ![Einar\_Raknes](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/einar_raknes/32/8566_2.png) [@Einar\_Raknes](https://forum.dynamobim.com/u/Einar_Raknes)\
**Post date:** [April 16, 2017, 3:42pm UTC](https://forum.dynamobim.com/t/creating-a-list-from-two-lists-with-all-possible-combinations-of-elements/11082/4 "2017-04-16T15:42:36Z")

</div>

> [@Ilya\_Kirichenko](#):
>
> But what’s the logic behind it? why concat and join don’t work?

Here is the explanation from one of the developers:

> [@Concatenate list of string](https://forum.dynamobim.com/t/concatenate-list-of-string/10354/8):
>
> @Einar_Raknes@Carlo_Beltracchi String.Join and String.Concat are based off of the .net class, string. The .net class has several overloads for both Join and Concat. [image] [image] Depending on what arguments you feed into the nodes, the system makes its best guess as to what you want to happen. The problem is that the UI doesn’t necessarily match what is happening in the backend. [image] For instance, both the String.Join and String.Concat nodes ask for string[] in the string0 input. Th…

---

_[View the full topic](https://forum.dynamobim.com/t/creating-a-list-from-two-lists-with-all-possible-combinations-of-elements/11082)._