Phema.Validation.AspNetCore 1.1.3

Phema.Validation

C# tiny, fast and customizable validation library

• Core library
• Extensions
• Conditions
• Tests
• AspNetCore integration

Validation

• Model

public class Person
{
  public string Name { get; set; }
  public int Age { get; set; }
}

• Validation

public class PersonValidation : IValidation<Person>
{
  public void Validate(IValidationContext validationContext, Person person)
  {
    validationContext.When(person, p => p.Name)
      .IsNullOrWhitespace()
      .AddError<PersonValidationComponent>(c => c.NameMustBeSet);
      
    validationContext.When(person, p => p.Name)
      .IsLess(2)
      .AddError<PersonValidationComponent>(c => c.NameIsShort);
      
    validationContext.When(person, p => p.Name)
      .IsGreater(20)
      .AddError<PersonValidationComponent>(c => c.NameIsLong);
      
    validationContext.When(person, p => p.Age)
      .IsNotGreater(18)
      .AddError<PersonValidationComponent>(c => c.Underage);
  }
}

• ValidationComponent

public class PersonValidationComponent : IValidationComponent<Person, PersonValidation>
{
  public PersonValidationComponent()
  {
    NameMustBeSet = new ValidationMessage(() => "Name must be set");
    NameIsShort = new ValidationMessage(() => "Name must be at least two characters");
    NameIsLong = new ValidationMessage(() => "Name must be not longer twenty characters");
    
    Underage = new ValidationMessage(() => "Age must be greater 18");
  }

  public ValidationMessage NameMustBeSet { get; set; }
  public ValidationMessage NameIsShort { get; set; }
  public ValidationMessage NameIsLong { get; set; }
  
  public ValidationMessage Underage { get; set; }
}

• Glue all together

services.AddPhemaValidation(validation => validation.Add<Person, PersonValidation, PersonValidationComponent>());

Using core

var validationContext = new ValidationContext();

// validationContext.When(nameof(model.Name), model.Name)
validationContext.When("key", "value")
  .Is(value => true)
  .Add(() => new ValidationMessage(() => "template"));
  
var error = Assert.Single(validationContext.Errors);

Assert.Equal("key", error.Key);
Assert.Equal("template", error.Message);

• This is a lightweight zero-dependent validation core
• You can add to Is callback any condition you want or even multiple of them (they will join using OR)
• You can store validation messages somewhere and pass them to Add callback or use extensions
• In Errors property you will find key (Property name or DataMember name override) and message (rendered after passing to Add callback)
• You can use parameterized validation messages adding arguments after in Add and placeholders ({0}, {1}) in template

Using extensions

var person = new Person
{
  Name = null
};

var validationContext = new ValidationContext();

validationContext.When(person, p => p.Name)
  .IsNullOrWhitespace()
  .Add(() => new ValidationMessage(() => "Is null or whitespace"));
  
var error = Assert.Single(validationContext.Errors);

Assert.Equal("Name", error.Key);
Assert.Equal("Is null or whitespace", error.Message);

• You can validate model value using expression like example above, or just passing T
• You can use predefined conditions like IsNot, IsNull, IsEmpty, etc.
• You can use Throw unstead or Add to stop execution flow. That will throw ValidationConditionException with Error property
• You can ensure that validation context is valid or throw ValidationContextException with Errors property by using EnsureIsValid
• You can validate that key in not presented in error using IsValid<T>(t => t.Key) or just passing string key
• You can use typed parameters (up to 2 for now) using Add<TArgument>(...) or Throw<TArgument>(...)

Using aspnetcore

public class TestModel
{
  public string Name { get; set; }
  public int Age { get; set; }
}

public class TestValidation : Validation<TestModel>
{
  private readonly TestValidationComponent component;
  
  public TestValidation(TestValidationComponent component)
  {
    this.component = component;
  }
		
  protected override void Validate(IValidationContext validationContext, TestModel model)
  {
    validationContext.When(model, m => m.Name)
      .IsNull()
      .Add(() => component.NameIsNull);

    validationContext.When(model, m => m.Age)
      .IsInRange(0, 17)
      .Add(() => component.IsUnderage);
  }
}
	
public class TestValidationComponent : ValidationComponent<TestModel, TestValidation>
{
  public TestValidationComponent()
  {
    NameIsNull = Register(() => "Name is null");
    IsUnderage = Register(() => "Is underage");
  }
  
  public ValidationMessage NameIsNull { get; }
  public ValidationMessage IsUnderage { get; }
}
  
// Startup
services.AddValidation(
  validation => 
    validation.Add<TestModel, TestValidation, TestValidationComponent>());

• You have to use mvc for validation, because validation uses filters for it
• You can inject IValidationContext to any part of your application
• You can override key by using [DataMember(Name = "key")] attribute
• You can add Validation without ValidationComponent or IValidationComponent without Validation, but i prefer not to do that because of responsibility
• If your validation context will be invalid after controller action executed, result will be substituted by validation messages. Try to check validation messages added explicitly by injection of IValidationContext before submiting changes