Expression language

Expressions are the small calculations and conditions that sit inside your logic: “is the opportunity worth more than 50,000?”, “the due date is three working days after the case was created”, “the customer’s mobile phone, or the business phone if there is none”. Logic Fabric uses one expression language everywhere, so what you learn once applies to logic blocks, logic flows and business processes alike.

You never type an expression as code. You build it in the expression editor by picking values and functions as cards and filling each function’s slots. The editor then shows the result as a readable formula, such as Days(createdon, Now) > 5, so you can check at a glance what you built.

Where you use expressions

Where	What the expression does	Learn more
Formula logic blocks	Calculates the block’s output value	Formula
Validations and validation sets	Decides whether a rule passes	Validation
Decision tables and decision trees	Checks the value in each condition cell or branch	Decision table, Decision tree
Logic flow steps	Supplies the value of a step input, a variable, or a step condition	Flow steps
Preconditions	Decides whether logic runs at all	Preconditions
Business process transitions and gateways	Decides which path a process takes	Transitions, Gateways and ends

Every place that takes an expression tells you the type of result it needs, for example a condition must result in Yes/No and a discount value must result in a number. The editor only lets you finish when the expression produces that type.

How building an expression works

1. Open the expression editor from the slot you want to fill. The panel header says what you are editing and what the result must be, for example Edit condition with Must result in Yes/No.
2. Pick a value or a function from the picker. Inputs and data from earlier steps are listed first, followed by constant values and the function categories.
3. If you picked a function, fill each of its slots the same way: pick an input, type a constant, or pick another function to nest inside it.
4. Watch the formula bar at the top. It shows the complete formula, its result type and whether there are problems left to fix.

For the full tour of the editor, including the outline, problem marking and the hover card, see The expression editor.

What is in the language

The picker groups more than 100 functions and operators into categories such as Text Functions, Math Functions, Date Functions, Collection Utilities and Choice Functions. Together they cover text and text patterns, numbers and rounding, dates and business days, list handling, currency conversion and security checks.

The expression editorPicker, slots, formula bar and problem marking.Data typesText, numbers, Currency, dates, choices, lookups and lists.Values and constantsInputs, step data, constants and configuration values.OperatorsArithmetic, comparisons and logical operators.Empty valuesHow each function treats a field that has no value.Calling logic blocksReuse a logic block inside an expression.

Function reference

All functionsThe complete catalog, grouped by category.TextJoin, split, format, patterns and encoding.NumbersArithmetic, rounding and currency conversion.Date and timeDate parts, date math, time zones and business days.ListsCount, sum, filter, sort and pick items.Logic and controlIf, And, Or, comparisons and checks.ConversionTurn text into numbers and Yes/No values.Choices and recordsFirst non-empty, Switch, option labels and record links.Users and securityCheck security roles and team membership.

On-premises labels

Logic Fabric for Dynamics 365 CE on-premises uses the classic Dataverse names for three types: Two Options instead of Yes/No, Entity instead of Row, and Option Set instead of Choice. These docs use the Dataverse labels. Everything else, including Currency and Lookup, is labelled the same in both editions.