Olve.Validation

Fluent validation helpers built on top of Olve.Results. Validators accumulate rules and return a Result containing all problems found.

Installation

dotnet add package Olve.Validation

Overview

Type	Description
`StringValidator`	String validation: null checks, length constraints, allowed/disallowed values.
`IntValidator`	Integer validation: numeric range, even/odd.
`DecimalValidator<T>`	Generic numeric validation for any `INumber<T>` type.
`EnumerableValidator<T>`	Collection validation: empty, duplicates, count.
`ListValidator<T>`	Optimized collection validation for `IList<T>`.
`IValidator<T>`	Interface for any validator that returns `Result`.
`IValidatable`	Interface for objects that can validate their own state.

Usage

String validation

Chain rules to build a validator, then call Validate() to get a Result.

// ../../tests/Olve.Validation.Tests/ReadmeDemo.cs#L12-L16

var result = new StringValidator()
    .CannotBeNullOrWhiteSpace()
    .MustHaveMinLength(3)
    .MustHaveMaxLength(50)
    .Validate("Alice");

When multiple rules fail, all problems are collected into the result:

// ../../tests/Olve.Validation.Tests/ReadmeDemo.cs#L24-L34

var result = new StringValidator()
    .CannotBeNullOrWhiteSpace()
    .MustHaveMinLength(3)
    .Validate("");

// Multiple rules can fail at once — all problems are collected
if (result.TryPickProblems(out var problems))
{
    foreach (var p in problems)
        Console.WriteLine(p.Message);
}

Numeric validation

IntValidator provides integer-specific rules like MustBeEven() and MustBeOdd() on top of the standard numeric range methods.

// ../../tests/Olve.Validation.Tests/ReadmeDemo.cs#L43-L46

var result = new IntValidator()
    .MustBePositive()
    .MustBeLessThan(100)
    .Validate(42);

DecimalValidator<T> works with any INumber<T> type (double, decimal, float, etc.):

// ../../tests/Olve.Validation.Tests/ReadmeDemo.cs#L54-L56

var result = new DecimalValidator<double>()
    .MustBeBetween(0.0, 1.0)
    .Validate(0.5);

Collection validation

// ../../tests/Olve.Validation.Tests/ReadmeDemo.cs#L64-L68

var result = new EnumerableValidator<string>()
    .CannotBeNull()
    .CannotBeEmpty()
    .CannotContainDuplicates()
    .Validate(new[] { "a", "b", "c" });

ListValidator<T> provides the same API optimized for IList<T>.

Custom error messages

Use WithMessage() or WithProblem() after a rule to override its default error:

// ../../tests/Olve.Validation.Tests/ReadmeDemo.cs#L76-L87

var result = new StringValidator()
    .CannotBeNullOrWhiteSpace()
    .WithMessage("Username is required")
    .MustHaveMinLength(3)
    .WithMessage("Username must be at least 3 characters")
    .Validate(null);

if (result.TryPickProblems(out var problems))
{
    foreach (var p in problems)
        Console.WriteLine(p.Message);
}

Integration with Olve.Results

Validators return Result, so they compose naturally with the rest of the Olve.Results API:

// ../../tests/Olve.Validation.Tests/ReadmeDemo.cs#L95-L104

Result ValidateEmail(string? email)
{
    return new StringValidator()
        .CannotBeNullOrWhiteSpace()
        .WithMessage("Email is required")
        .Validate(email);
}

var valid = ValidateEmail("user@example.com");
var invalid = ValidateEmail(null);

Documentation

Full API reference: https://olivervea.github.io/Olve.Utilities/api/Olve.Validation.html