Skip to main content
cancel
Showing results for 
Search instead for 
Did you mean: 

Vote for your favorite vizzies from the Power BI Dataviz World Championship submissions. Vote now!

Reply
lily99
Regular Visitor

API call a list in M query

Hello,

I want to build a Body of a REST API call using M Query in PowerBI. 

I have a list of ID from a list named "UserID" that I want to use it as a variable in the body

 

Here is my script

body = "{""ids"":" & List.Distinct(UserID) & "}",

 

When I executed it, it gave me an errors:

Expression.Error: We cannot apply operator & to types Text and List.
Details:
Operator=&
Left={"ids":
Right=[List]

 

How can I handle this error? what can be a workaround?

 

Thanks for your help.

1 ACCEPTED SOLUTION
CNENFRNL
Community Champion
Community Champion

@lily99 , you might want to try

body = "{""ids"":[" & Text.Combine(List.Transform(List.Distinct(UserID), each """" & _ & """"),",") & "]}"

Screenshot 2021-02-05 050430.png


Thanks to the great efforts by MS engineers to simplify syntax of DAX! Most beginners are SUCCESSFULLY MISLED to think that they could easily master DAX; but it turns out that the intricacy of the most frequently used RANKX() is still way beyond their comprehension!

DAX is simple, but NOT EASY!

View solution in original post

4 REPLIES 4
lily99
Regular Visitor

Hello @ImkeF 

Thanks for your suggestion, I applied it.

body = "{""ids"":[""" & Text.Combine(List.Distinct(UserID),",") & """]}"

 

and get the result

{"ids":["User1,User2,User3,User4"]}

 

However, I want to have the result like this:

{"ids":["User1","User2","User3","User4"]}

 

so I applied  extra "" around the list

= "{""ids"":[" & Text.Combine({"""",List.Distinct(UserID),""""},",") & "]}"

and I got this error:

Expression.Error: We cannot convert a value of type List to type Text.
Details:
Value=[List]
Type=[Type]

 

How can I make my body return like this?

{"ids":["User1","User2","User3","User4"]}

 

Thanks alot 

CNENFRNL
Community Champion
Community Champion

@lily99 , you might want to try

body = "{""ids"":[" & Text.Combine(List.Transform(List.Distinct(UserID), each """" & _ & """"),",") & "]}"

Screenshot 2021-02-05 050430.png


Thanks to the great efforts by MS engineers to simplify syntax of DAX! Most beginners are SUCCESSFULLY MISLED to think that they could easily master DAX; but it turns out that the intricacy of the most frequently used RANKX() is still way beyond their comprehension!

DAX is simple, but NOT EASY!

Thanks so much @CNENFRNL . It worked perfectly!

ImkeF
Community Champion
Community Champion

Hi @lily99 ,

if you want to pass a string into the body, you'd have to transform the list into a string as well. Meaning, concatenate the values by comma for example:

 

body = "{""ids"":" & Text.Combine(List.Distinct(UserID), ",") & "}",


 

Imke Feldmann (The BIccountant)

If you liked my solution, please give it a thumbs up. And if I did answer your question, please mark this post as a solution. Thanks!

How to integrate M-code into your solution -- How to get your questions answered quickly -- How to provide sample data -- Check out more PBI- learning resources here -- Performance Tipps for M-queries

Helpful resources

Announcements
Power BI DataViz World Championships

Power BI Dataviz World Championships

Vote for your favorite vizzies from the Power BI World Championship submissions!

Sticker Challenge 2026 Carousel

Join our Community Sticker Challenge 2026

If you love stickers, then you will definitely want to check out our Community Sticker Challenge!

January Power BI Update Carousel

Power BI Monthly Update - January 2026

Check out the January 2026 Power BI update to learn about new features.

FabCon Atlanta 2026 carousel

FabCon Atlanta 2026

Join us at FabCon Atlanta, March 16-20, for the ultimate Fabric, Power BI, AI and SQL community-led event. Save $200 with code FABCOMM.