📘 Net.Extensions.FormsValidation

Declarative, decoupled, and UI-agnostic validation framework for .NET applications

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🎯 Goal

Net.Extensions.FormsValidation decouples validation logic from UI components, offering a fluent, reusable, and strongly-typed way to define validation rules for any data type. It's compatible with WinForms, WPF, Blazor, ASP.NET Core, Maui, and any other .NET UI or data-based technology.

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🧱 Architecture

Component	Description
FormValidator	Main coordinator that registers fields and triggers validation.
Validator<T>	Core component to compose rules for type T.
ValidationResult	Represents the result of a validation with severity and message.
ValidationRule<T>	Individual rule implementing logic for a Validator<T>.
Extensions (*.Extensions)	Extension methods providing ready-to-use rules.

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🧪 Usage Example

var formValidator = new FormValidator();

var nameValidator = Validator<string>
    .Create()
    .Required("Name is required")
    .MinLength(3, "Minimum 3 characters")
    .MaxLength(50);

var ageValidator = Validator<int>
    .Create()
    .GreaterThan(17, "Must be an adult")
    .LessThanOrEqualTo(99);

formValidator.AddFieldValidator("Name", () => nameInput.Text, nameValidator);
formValidator.AddFieldValidator("Age", () => int.Parse(ageInput.Text), ageValidator);

var result = formValidator.Validate();

if (!result.IsValid)
{
    Console.WriteLine(result.Message); // Or display it in the UI
}

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🧩 Available Extensions

📄 Text (string)

• .Required()
• .MinLength(int) / .MaxLength(int) / .Length(min, max)
• .Email()
• .UrlRule()
• .StartsWith(), .EndsWith(), .Contains(), .NotContains()
• .Regex()

🔢 Numbers (int, double, etc.)

• .GreaterThan(), .GreaterThanOrEqualTo()
• .LessThan(), .LessThanOrEqualTo()
• .EqualTo(), .NotEqualTo()
• .Range(min, max)

🕒 Dates (DateTime)

• .PastDateRule()
• .FutureDateRule()
• .DateRange(min, max)

🧺 Collections (ICollection<object>, lists, arrays)

• .NotEmpty()
• .MinCount(int) / .MaxCount(int)
• .AnyMatch(predicate) / .AllMatch(predicate)

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✅ ValidationResult

Simple class representing the result of a validation:

public class ValidationResult
{
    public bool IsValid => Severity == null;
    public ValidationSeverity? Severity { get; }
    public string Message { get; }

    public static ValidationResult Success() => new ValidationResult();
    public static ValidationResult Fail(string message, ValidationSeverity severity = ValidationSeverity.Error)
        => new ValidationResult(severity, message);
}

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🔌 UI Integration (Examples)

WinForms

var validator = new FormValidator();
var emailValidator = Validator<string>
    .Create()
    .Required("Email is required")
    .Email("Invalid email");

validator.AddFieldValidator("Email", () => emailTextBox.Text, emailValidator);

var result = validator.Validate();
if (!result.IsValid)
{
    MessageBox.Show(result.Message);
}

Blazor

<EditForm OnValidSubmit="Validate">
    <InputText @bind-Value="Model.Email" class="form-control" />
    <ValidationMessage For="@(() => Model.Email)" />
    <button type="submit">Validate</button>
</EditForm>

@if (!string.IsNullOrEmpty(ErrorMessage))
{
    <p class="text-danger">@ErrorMessage</p>
}

@code {
    private FormValidator validator = new();
    private string ErrorMessage = string.Empty;
    private MyModel Model = new();

    protected override void OnInitialized()
    {
        var emailValidator = Validator<string>
            .Create()
            .Required("Email is required")
            .Email("Invalid email format");

        validator.AddFieldValidator("Email", () => Model.Email, emailValidator);
    }

    void Validate()
    {
        var result = validator.Validate();
        ErrorMessage = result.IsValid ? string.Empty : result.Message;
    }

    public class MyModel
    {
        public string Email { get; set; } = string.Empty;
    }
}

WPF

var validator = new FormValidator();
var nameValidator = Validator<string>
    .Create()
    .Required("Name is required")
    .MinLength(2);

validator.AddFieldValidator("Name", () => NameTextBox.Text, nameValidator);

var result = validator.Validate();
if (!result.IsValid)
{
    MessageBox.Show(result.Message);
}

ASP.NET Core (MVC)

public class MyModel
{
    public string Email { get; set; } = string.Empty;
}

[HttpPost]
public IActionResult Submit(MyModel model)
{
    var validator = new FormValidator();
    var emailValidator = Validator<string>
        .Create()
        .Required("Email is required")
        .Email("Invalid email");

    validator.AddFieldValidator("Email", () => model.Email, emailValidator);

    var result = validator.Validate();
    if (!result.IsValid)
    {
        ModelState.AddModelError("Email", result.Message);
        return View(model);
    }

    // Proceed normally
    return RedirectToAction("Success");
}

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🧱 Key Benefits

• ✅ Fully decoupled from the UI
• 🧪 Composable and reusable validations
• 🔄 Easy to integrate with any architecture (MVVM, MVP, etc.)
• ♻️ Reusable in services, APIs, and business logic

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🚧 Roadmap

• Async validation support
• Sectioned/grouped field validation
• Error message localization
• Direct support for IValidationAttribute

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🗂️ Main Namespaces

• Net.Extensions.FormsValidation
• Net.Extensions.FormsValidation.Extensions
• Net.Extensions.FormsValidation.Rules
• Net.Extensions.FormsValidation.Enums

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📦 Installation (coming soon to NuGet)

dotnet add package JoeDevSharp.Net.Extensions.FormsValidation

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Built for developers seeking modern, fluent, and decoupled validation in any .NET stack.

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