What do I need to do to make a custom function appear in the DAX dropdown list

[neilmacmullen]

I have created a new power-query function by selecting Home->Edit Queries->New Source->Blank Queries->Advanced Editor.

The function shows up in the query list and I can invoke it from the query editor.

I then click "close and apply"

I was expecting the newly named function to then appear amongst the DAX dropdown/intellisense list when creating a new calculated column or measure but it doesn't.  If I write the name of the function in the expression, I just get a syntax error.

Am I missing a step?  None of the custom function tutorials I've found  show a new function being invoked from the main application - is it even possible?  (I'm not sure how you would be able to write reusable functions without this though?)

[garythomannCoGC]

Custom (Reusable) DAX Function   please vote :}

[ImkeF · Accepted solution]

Custom functions are created using the M-language and can only be used in the query editor (where the M-language is used).

You cannot write custom functions in/for DAX.

This video shows how to reuse M-functions: https://www.youtube.com/watch?v=6TQN6KPG74Q

[neilmacmullen]

Thanks Imke.  I'd worked out that M and custom functions were probably the way to go to solve my _actual_ problem (https://community.powerbi.com/t5/Desktop/Working-with-time-based-IOT-data-in-PowerBi-advice-needed/m...) but was clearly suffering a major misunderstanding in thinking that power queries were also a way of extending the set of operations available in the DAX editor in the report view.   It seems very odd not to have some way of providing resuable code/patterns in the report view  - it seems that once I start writing M code I'll be forever relegated to the query-editor.   😞 

Anyway, thanks for the video link - I'll definitely check out the blog and the repo looks like an excellent reference source for someone trying to learn M. 

Even though this is not the answer I was hoping to hear, I'll mark it as a solution 🙂