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edhans's avatar
edhans
Community Champion
6 years ago
Solved

Understanding Expression.Evaluate - isn't working

I have the following M code:     let Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WUtJR8krMUzAyMDJQitUB88G0Z0lqLpAdnJiTWgwWSATyDMGsJCDLCMxKBrKMlWJjAQ==", Bin...
Need Help
  • artemus's avatar
    artemus
    6 years ago

    When you use Expression.Evaulate you need to include every variable and library function you want to make avialable in a record. In your case:

    Expression.Evaulte(#"Need Help", [Long Step Name = #"Long Step Name"])

     

ImkeF's avatar
ImkeF
Community Champion
6 years ago

Hi edhans ,

My friend LarsSchreiber  and I have written an article about the evaluation context in M that might explain a bit of this here (hopefully 😉  ) https://ssbi-blog.de/blog/technical-topics-english/the-environment-concept-in-m-for-power-query-and-power-bi-desktop-part-3/

 

You can find the official language specification here now: https://docs.microsoft.com/en-us/powerquery-m/power-query-m-language-specification

 

BTW: The "equivalent" of Table.Column is Record.Field (if you want to do some dynamic field referencing on row-level) 

 

 

edhans's avatar
edhans
Community Champion
6 years ago

Thanks ImkeF for the reminder on Record.Field. I've used it before but not enough I could just code with it, so need to go back and refresh my memory with it.

 

So many ways to do the same or similar things in Power BI, but performance considerations, or just code readability, can be very different. 👍