Phema.Validation 3.1.4

Phema.Validation

A simple, lightweight and extensible validation library for .NET Core with fluent interfaces built using extension methods only

Installation

$> dotnet add package Phema.Validation

Core concepts

• IValidationContext - Scoped service to store all validation details
• IValidationCondition - Contains a validation checks (e.g. Is(() => ...))
• IValidationDetail - When IValidationCondition is not valid adds to IValidationContext.ValidationDetails
• ValidationSeverity - Validation error level, used in IValidationContext.ValidationSeverity and IValidationDetail.ValidationSeverity
• IValidationScope - Is a nested validation context with validation path override

Usage (ASP.NET Core, HostedService examples)

// Add `IValidationContext` as scoped service
services.AddValidation(options => ...);

// Get or inject
var validationContext = serviceProvider.GetRequiredService<IValidationContext>();

// Validation key will be `Name` using default validation part provider
validationContext.When(person, p => p.Name)
  .Is(name => name == null)
  .AddError("Name must be set");

// Validation key will be `Address.Locations[0].Latitude` using default validation part provider
validationContext.When(person, p => p.Address.Locations[0].Latitude)
  .Is(latitude => ...custom check...)
  .AddError("Some custom check failed");

Validation conditions

• Monads are not composable, so Is and IsNot, IsNull and IsNotNull... duplication

// Check for Phema.Validation.Conditions namespace
validationContext.When(person, p => p.Name)
  .IsNullOrWhitespace()
  .AddError("Name must be set");

// Use multiple conditions (joined with AND)
validationContext.When(person, p => p.Name)
  .IsNotNull()
  // AND
  .HasLengthGreater(20)
  // .IsNull()
  // .IsEqual()
  // .IsNotUrl()
  // .IsNotEmail()
  // .IsMatch(regex)
  .AddError("Name should be less than 20");

Validation details

// Null if valid
var validationDetails = validationContext.When(person, p => p.Age)
  // Validation condition is valid
  .Is(() => false)
  .AddError("Age must be set");

// Use deconstruction
var (key, message) = validationContext.When(person, p => p.Age)
  .IsNull()
  .AddError("Age must be set");

// More deconstruction
var (key, message, severity) = validationContext.When(person, p => p.Age)
  .IsNull()
  .AddError("Age must be set");

Check validation

// Override default ValidationSeverity
validationContext.ValidationSeverity = ValidationSeverity.Warning;

// Throw exception when details severity greater than ValidationContext.ValidationSeverity
validationContext.When(person, p => p.Address)
  .IsNull()
  .AddFatal("Address is not presented!!!"); // If invalid throw ValidationConditionException

// Check if context is valid
validationContext.IsValid();
validationContext.EnsureIsValid(); // If invalid throw ValidationContextException

// Check concrete validation details
validationContext.IsValid(person, p => p.Age);
validationContext.EnsureIsValid(person, p => p.Age);

Compose and reuse validation rules with extensions

• Call is allocation free
• Static checks

// Extensions
public static void ValidateCustomer(this IValidationContext validationContext, Customer customer)
{
  // Some checks
}

validationContext.ValidateCustomer(customer);

• Write your own middleware or validation components/validators on top of IValidationContext

Validation part resolvers

• ValidationPartResolver is a delegate, trying to get string valdiation part from MemberInfo
• Use built in resolvers with ValidationPartResolvers static class: Default, DataMember, PascalCase, CamelCase

// Configure DataMember validation part resolver
services.AddValidation(options =>
  options.ValidationPartResolver = ValidationPartResolvers.DataMember);

// Override validation parts with `DataMemberAttribute`
[DataMember(Name = "name")]
public string Name { get; set; }

Validation scopes

• Use scopes when you need to have:
  • Same nested validation path multiple times
  • Empty validation details collection (syncing with parent context/scope)
  • ValidationSeverity override

// Validation key will be `Child.*ValidationPart*`
ValidateChild(validationContext.CreateScope(parent, p => p.Child))

// Validation key will be `Address.Locations[0].*ValidationPart*`
ValidateLocation(validationContext.CreateScope(person, p => p.Address.Locations[0]))

// Override local scope ValidationSeverity
using (var scope = validationContext.CreateScope(person, p => p.Address))
{
  scope.ValidationSeverity = ValidationSeverity.Warning;

  // Some scope validation checks syncing with validationContext
}

High performance with non-expression constructions

validationContext.When("key", value)
  .IsNull()
  .AddError("Value is null");

validationContext.CreateScope("key");

validationContext.IsValid("key");
validationContext.EnsureIsValid("key");