Triplex

Validation library inspired by the concepts of Secure by Design, by Dan Bergh Johnsson, Daniel Deogun, and Daniel Sawano (MEAP 2019 Manning Publications). (Preconditions, Postconditions, Invariants & Proto-Primitives at https://docs.microsoft.com/en-us/dotnet/framework/debug-trace-profile/code-contracts)

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Types of validations

Arguments

Remember that arguments are actual values to methods declared parameters. The utility class used to validate arguments is Triplex.Validations.Arguments. If an argument is invalid this utility will throw an System.ArgumentException or one of its derivatives.

Object's state

Sometimes we need to check internal state before or after certain operation to ensure preconditions and invariants respectively. To check for those we use Triplex.Validation.State utility. This one throws System.InvalidOperationException or one of its derivatives.

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Examples

Arguments

using Triplex.Validations;

public sealed class Email
{
	private readonly string _value;

	public Email(string value) {
		Arguments.NotNull(value);
		Arguments.LengthBetween(value, 12, 60);
		Arguments.MatchesPattern(value.ToLowerInvariant(), "^[a-zA-Z.][email protected]$");
		
		_value = value.ToLowerInvariant();
	}
}

All methods has three forms:

1. Data only, no argument name, nor custom message. Like Arguments.NotNull(someArg);
2. Data, argument name, but no custom message. Like Arguments.NotNull(someArg, nameof(someArg));
3. Data, argument name, and custom message. Like Arguments.NotNull(someArg, nameof(someArg), "Your custom exception message goes here");

Object's state

using Triplex.Validations;

public sealed class Point
{
	//private Point stuff here...

	//Useful constructor(s) here
	//public Point(...) { }

	public void MoveBy(int x, int y, int z) {
		//1. Any relevant arguments validations here using Arguments util
		Arguments.All(x, y, z).NotEqualTo(default(int));

		//2. Do your stuff
		ComplexMoveLogic(x, y, z);
		
		//3. Afther moving, could not be outside map's boundaries
		State.StillHolds(_theMap.IsStrictlyWithin(this)); // throws if false
	}
}

All methods has two forms:

1. Data only, no custom message. Like State.StillHolds(somePostActionValidation);
2. Data, argument name, but no custom message. Like State.StillHolds(somePostActionValidation, "Your custom exception message goes here");

There is no argument name, because State is used to validate objects internal state, as a hole, or invariants.

We like to get help from everybody, if you want to contribute to this tool, found some issue or just want a feature request please read, first, the Contributing guide.