FEEL-like Helpers

EasyDecisions provides a set of extension methods that mimic the syntax of FEEL (Friendly Enough Expression Language), the expression language used in DMN (Decision Model and Notation).

These helpers make your C# decision rules more readable and closer to "Business Language".

Why use them?

In standard C#, range checks and list checks can become verbose:

// Standard C#
.When(x => x.Age >= 18 && x.Age <= 65)
.When(x => x.Status == "Active" || x.Status == "Pending")

With FEEL-like Helpers, these become much more expressive:

using EasyDecisions.Extensions;

// Expressive business rules
.When(x => x.Age.IsBetween(18, 65))
.When(x => x.Status.IsIn("Active", "Pending"))

Available Helpers

Range Checks

Method	FEEL Equivalent	Description
IsBetween(min, max)	[min..max]	Inclusive range check.
IsBetweenExclusive(min, max)	(min..max)	Exclusive range check.
IsBetween(min, max, incMin, incMax)	Mixed	Configurable inclusivity (e.g., [min..max)).
IsAtLeast(min)	>= min	Greater than or equal to.
IsAtMost(max)	<= max	Less than or equal to.
IsGreaterThan(min)	> min	Strictly greater than.
IsLessThan(max)	< max	Strictly less than.

Examples

// Age between 18 and 65 (inclusive)
x => x.Age.IsBetween(18, 65)

// Score strictly between 0 and 100
x => x.Score.IsBetweenExclusive(0, 100)

// Age is at least 18
x => x.Age.IsAtLeast(18)

Collection Checks

Method	FEEL Equivalent	Description
IsIn(params items)	x in (a, b, c)	Checks if the value is in the list.
IsIn(IEnumerable)	x in list	Checks if the value is in a collection.
IsNotIn(params items)	not(x in (a, b, c))	Checks if the value is NOT in the list.

Examples

// Category is one of the allowed values
x => x.Category.IsIn("Electronics", "Books", "Toys")

// Status is NOT 'Expired' or 'Cancelled'
x => x.Status.IsNotIn("Expired", "Cancelled")

Supported Types

These helpers work on any type that implements IComparable<T>, including:

• int, long, decimal, double, float
• string
• DateTime, DateTimeOffset
• TimeSpan
• Custom types implementing IComparable<T>