# List.combine node outputting null lists

**URL:** <https://forum.dynamobim.com/t/list-combine-node-outputting-null-lists/110914>\
**Category:** DesignScript\
**Tags:** dynamo\
**Created:** [June 24, 2025, 9:42pm UTC](https://forum.dynamobim.com/t/list-combine-node-outputting-null-lists/110914 "2025-06-24T21:42:04Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![OABDELLATIF05](https://avatars.discourse-cdn.com/v4/letter/o/c2a13f/32.png) [@OABDELLATIF05](https://forum.dynamobim.com/u/OABDELLATIF05)\
**Post date:** [June 24, 2025, 9:42pm UTC](https://forum.dynamobim.com/t/list-combine-node-outputting-null-lists/110914/1 "2025-06-24T21:42:04Z")

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Hey,

I’m new to Dynamo and I am curious as to why my list.combine is outputting null instead of values. My original goal is to use List.Cartesianproduct by I found that this is also an issue with List.Combine and I am assuming for the same reason. I’ve tried a couple things but I feel like the answer is much simpler than I believe.

Any help would be appreciated.

 ![image](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/b/5/b5abefd54e532d83eae12525e2d80ee972ac8ef9.png)

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**Author:** ![jacob.small](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/jacob.small/32/161030_2.png) [@jacob.small](https://forum.dynamobim.com/u/jacob.small)\
**Post date:** [June 24, 2025, 11:52pm UTC](https://forum.dynamobim.com/t/list-combine-node-outputting-null-lists/110914/2 "2025-06-24T23:52:28Z")

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I think you want List.AddItemToFront with levels set to @L1, and skip the List.Combine.

The first input to the node should be a function (the node Object.Type can tell you what you have from another nodes output). I believe you are providing a null object at the moment as DesignScript cannot author functions like this.

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**Author:** ![Mike.Buttery](https://avatars.discourse-cdn.com/v4/letter/m/b19c9b/32.png) [@Mike.Buttery](https://forum.dynamobim.com/u/Mike.Buttery)\
**Post date:** [June 24, 2025, 11:58pm UTC](https://forum.dynamobim.com/t/list-combine-node-outputting-null-lists/110914/3 "2025-06-24T23:58:03Z")

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_List.Combine_ will not see the designscript as a function, use a node to drive the combination. You will have to add an input port on the function node to match the combine node

 ![list_combine](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/d/7/d7467676276e6f467cc27ea965b290672eb16f10.png)