NContract - a design by contract library for .NET

NContract lets you write one-liners to verify parameters in constructors and methods instead of using more verbose if statements.

Installation

Add the Nuget package NContract by using your IDE or through the terminal:

dotnet add package NContract

Usage

Null checks

To verify that a parameter is not null:

Require.NotNull(parameter, nameof(parameter));

To verify that a parameter is null:

Require.Null(parameter, nameof(parameter));

Strings

To verify that a parameter is not null or empty:

Require.NotNullOrEmpty(parameter, nameof(parameter));

To verify that a parameter is not null or whitespace:

Require.NotNullOrWhitespace(parameter, nameof(parameter));

True or false conditions

To verify that a parameter value is true to a condition, for example >= 10:

Require.True(parameter >= 10, "Parameter must be 10 or greater", nameof(parameter));

To verify that a parameter value is false to a condition, for example >= 10:

Require.False(parameter >= 10, "Parameter must be 9 or less", nameof(parameter));

Collections

To verify that a parameter is not empty:

Require.NotEmpty(parameter, nameof(parameter));

To verify that a parameter is empty:

Require.Empty(parameter, nameof(parameter));

To verify that a parameter value has at least one element satisfying a predicate, for example >= 10:

Require.Any(parameter, v => v >= 10, "At least one parameter element must be 10 or greater", nameof(parameter));

To verify that all parameter values satisfies a predicate, for example >= 10:

Require.All(parameter, v => v >= 10, "All parameter elements must be 10 or greater", nameof(parameter));

To verify that no parameter values matches a predicate, for example >= 10:

Require.None(parameter, v => v >= 10, "No parameter elements can be 10 or greater", nameof(parameter));

Implements type checks

To verify that a parameter value implements a type T:

Require.Implements<T>(parameter, nameof(parameter)");

License

This project is licensed under the MIT license. See the LICENSE file for more info.