Abstractions

Core contracts and shared types for the Dosaic validation subsystem. This package defines the interfaces that all validation plugin implementations must fulfil, along with the result model and a rich set of predefined validation-error codes.

Installation

dotnet add package Dosaic.Plugins.Validations.Abstractions

Types

IValidator

The top-level validation entry point. Accepts a model or an explicit list of IValueValidator instances and returns a ValidationResult.

public interface IValidator
{
    // Validate a model using its own declared validators
    Task<ValidationResult> ValidateAsync(object model, CancellationToken cancellationToken = default);

    // Strongly-typed convenience overload
    Task<ValidationResult> ValidateAsync<T>(T model, CancellationToken cancellationToken = default);

    // Validate a single value against an explicit validator list
    Task<ValidationResult> ValidateAsync(object value, IList<IValueValidator> validators, CancellationToken cancellationToken = default);
}

---

IValueValidator

Represents a single validation rule applied to one value. Implementations carry their own error message, a structured error code, optional arguments, and a null-handling policy.

public interface IValueValidator
{
    string ErrorMessage { get; }
    string Code { get; }
    object Arguments { get; }
    bool TreatNullAsValid { get; }
    Task<bool> IsValidAsync(ValidationContext context, CancellationToken cancellationToken = default);
}

Member	Description
ErrorMessage	Human-readable description of the constraint violation
Code	Machine-readable error code (see ValidationCodes)
Arguments	Arbitrary object whose public properties are surfaced in ValidationError.Arguments
TreatNullAsValid	When true (default), a null value skips this validator
IsValidAsync	Returns true when the value in context satisfies the rule

---

ValidationContext

Immutable record passed into every IValueValidator.IsValidAsync call.

public sealed record ValidationContext(object Value, string Path, IServiceProvider Services);

Member	Description
Value	The value being validated
Path	Dot-notation property path, e.g. "Address.PostalCode"
Services	The application IServiceProvider for service-dependent validators
ValueType	Value.GetType() — null-safe
IsNullValue	true when Value is null
IsObjectType	true for plain class instances (not string, not collection, not dictionary)
IsListType	true for any IEnumerable that is not a string

---

ValidationResult

Returned by every IValidator.ValidateAsync call.

public class ValidationResult
{
    public required ValidationError[] Errors { get; init; }
    public bool IsValid => Errors.Length == 0;
}

---

ValidationError

Describes a single constraint violation.

public class ValidationError
{
    public required string Validator { get; init; }
    public required IDictionary<string, object> Arguments { get; init; }
    public required string Path { get; init; }
    public required string Code { get; init; }
    public required string Message { get; init; }
}

Property	Description
Validator	Name of the IValueValidator that produced this error
Arguments	Key/value pairs from the validator's Arguments object
Path	Property path where the violation occurred
Code	Structured error code from ValidationCodes
Message	Human-readable error message from the validator

---

ValidationCodes

A static hierarchy of well-known, string-typed error-code constants used by all built-in validators.

Category	Constant	Code value
(root)	GenericError	"InternalError"
(root)	Required	"Required"
(root)	Expression	"Expression"
(root)	Unique	"Unique"
(root)	InvalidType	"InvalidType"
String	MinLength	"String.MinLength"
String	MaxLength	"String.MaxLength"
String	Length	"String.Length"
String	Regex	"String.Regex"
String	Email	"String.Email"
String	Url	"String.Url"
Int	Range	"Number.Range"
Int	Min	"Number.Min"
Int	Max	"Number.Max"
Int	Negative	"Number.Negative"
Int	Positive	"Number.Positive"
Date	Before	"Date.Before"
Date	After	"Date.After"
Date	Age	"Date.Age"
Date	MinAge	"Date.MinAge"
Date	MaxAge	"Date.MaxAge"
Bool	True	"Bool.True"
Bool	False	"Bool.False"
Array	Length	"Array.Length"
Array	MinLength	"Array.MinLength"
Array	MaxLength	"Array.MaxLength"

---

ValueValidatorExtensions

Extension methods that simplify working with IValueValidator implementations.

Method	Description
GetArguments(this IValueValidator)	Reflects over Arguments and returns a Dictionary<string, object> of its public properties
GetName(this IValueValidator)	Returns the validator's class name, stripping a trailing Attribute suffix when present

Usage

Injecting and using IValidator

public class CreateUserHandler(IValidator validator)
{
    public async Task HandleAsync(CreateUserRequest request, CancellationToken ct)
    {
        var result = await validator.ValidateAsync(request, ct);
        if (!result.IsValid)
        {
            foreach (var error in result.Errors)
                Console.WriteLine($"[{error.Code}] {error.Path}: {error.Message}");

            return;
        }

        // proceed with valid request …
    }
}

Implementing a custom IValueValidator

using Dosaic.Plugins.Validations.Abstractions;

public class PositiveNumberValidator : IValueValidator
{
    public string ErrorMessage => "Value must be a positive number";
    public string Code => ValidationCodes.Int.Positive;
    public object Arguments => new { };
    public bool TreatNullAsValid => true;

    public Task<bool> IsValidAsync(ValidationContext context, CancellationToken cancellationToken = default)
    {
        if (context.IsNullValue) return Task.FromResult(true);
        if (context.Value is int i) return Task.FromResult(i > 0);
        return Task.FromResult(false);
    }
}

Validating a value against an explicit validator list

var validators = new List<IValueValidator> { new PositiveNumberValidator() };
var result = await validator.ValidateAsync(userInput, validators, ct);

if (!result.IsValid)
    Console.WriteLine(result.Errors[0].Message);

Inspecting a validator via extensions

IValueValidator v = new PositiveNumberValidator();

var name = v.GetName();                   // "PositiveNumber"
var args = v.GetArguments();              // Dictionary<string, object>