Apply custom validators

Requires: abstractions module, main module (constraints).

Validation feature allows to associate a custom user-made validator with a settings type. Validation occurs during binding and results in binding errors for incorrect settings.

[ValidateBy(typeof(MySettingsValidator))]
class MySettings
{
    int CacheCapacity { get; }
}

class MySettingsValidator: ISettingsValidator<MySettings>
{
    // Returns validation errors. Empty enumerable == success.
    public IEnumerable<string> Validate(MySettings settings)
    {
        if (settings.CacheCapacity <= 0)
            yield return "Cache capacity must be positive.";
    }
}

Constraints

There are also built-in validation constraints you can use to create a custom validator. Just inherit your validator class from ConstraintsValidator and override a method returning constraints to be checked:

[ValidateBy(typeof(TestConfigValidator))]
class TestConfig
{
    public int Number;
    public string String;
}

class TestConfigValidator : ConstraintsValidator<TestConfig>
{
    protected override IEnumerable<Constraint<TestConfig>> GetConstraints()
    {
        yield return new NotNullOrWhitespaceConstraint<TestConfig>(settings => settings.String);
        yield return new RangeConstraint<TestConfig, int>(settings => settings.Number, 2, 10);
    }
}

Here's a list of all currently implemented constraint types:

• NotNullConstraint for arbitrary reference types;

• NotNullOrEmptyConstraint for strings;

• NotNullOrWhitespaceConstraint for strings;

• RangeConstraint, LessConstraint, LessOrEqualConstraint, GreaterConstraint and GreaterOrEqualConstraint for any types that implement IComparable;

• UniqueConstraint to check that a set of field/properties only contains unique values;

Related pages

Obtain settings from providerBinding nodes to models