Marco Russo and Alberto Ferrari look at a new feature in DAX:
Although DAX is a functional language, it did not previously offer the option to let users define their own functions. Starting from the September 2025 version, it is possible to define functions, which are parametrized expressions that can be reused throughout the entire semantic model. This article explains how the functions work. Watch the related video to see the user interface for defining functions.
Click through for more information, and also check out SQLBI’s DAX Lib website for a few examples of the types of user-defined functions you can create.