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Metalama.Patterns.Contracts 2026.1.18

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About

The Metalama.Patterns.Contracts package implements the concept of contract-based programming, encompassing preconditions, postconditions, and invariants.

Key Features

• Implementation of preconditions and postconditions through a wide range of numeric or string-based contracts.
• Verification of invariants.

Main Types

Below is a list of available contract attributes for your selection:

Nullability Contracts

• [NotNull] verifies that the assigned value is not null.
• [Required] contract verifies that the value is not null and requires the string to be non-empty.

String Contracts

• [NotEmpty] requires the string to be non-empty. Note that this contract does not validate the string against being null. If you want to prohibit both null and empty strings, use [Required].
• [CreditCard] validates that the string is a valid credit card number.
• [Email], [Phone], and [Url] validate strings against well-known regular expressions.
• [Regex] validates a string against a custom regular expression.
• [StringLength] validates that the length of a string falls within a specified range.

Enum Contracts

• [EnumDataType] contract can validate values of type string, object, or of any integer type. It throws an exception if the value is not valid for the given enum type.

Numeric Contracts

The following contracts can be used to verify that a value falls within a specified range:

• [LessThan] verifies that the value is less than or equal to the specified maximum.
• [GreaterThan] verifies that the value is greater than or equal to the specified minimum.
• [Negative] verifies that the value is less than or equal to zero.
• [Positive] verifies that the value is greater than or equal to zero.
• [Range] verifies that the value is greater than or equal to a specified minimum and less than or equal to a specified maximum.
• [StrictlyLessThan] verifies that the value is strictly less than the specified maximum.
• [StrictlyGreaterThan] verifies that the value is strictly greater than the specified minimum.
• [StrictlyNegative] verifies that the value is strictly less than zero.
• [StrictlyPositive] verifies that the value is strictly greater than zero.
• [StrictRange] verifies that the value is strictly greater than a specified minimum and strictly less than a specified maximum.

Collections Contracts

• [NotEmpty] contract can be used on any collection, including arrays or immutable arrays. It requires the collection or the array to contain at least one element.

Invariants

• [Invariant] causes the target method (a parameterless void method) to be invoked after each public method or property setter.
• [DoNotCheckInvariants] exempts the target method from enforcing invariants, but does not exempt any method or property setter used by this method.
• [SuspendInvariant] exempts the target method from enforcing invariants, including any method or property setter used by this method.

Additional Documentation

• Conceptual documentation:
  • Preconditions and postconditions
  • Invariants
• API documentation