Fluent Validation with Swagger in Asp.net Core - asp.net-core

Question

I am currently using Fluent Validation instead of Data Annotations for my Web api and using swagger for API documentation. Fluent validation rules are not reflected in swagger model as i am unable to configure fluent validation rules with swagger schema filter.
This Blog has a good explanation for using it with ASP.net MVC. but i am unable to configure it to use it in ASP.net Core.
So far i have tried the following code but i am unable to get validator type.
services.AddSwaggerGen(options => options.SchemaFilter<AddFluentValidationRules>());
public class AddFluentValidationRules : ISchemaFilter
{
public void Apply(Schema model, SchemaFilterContext context)
{
model.Required = new List<string>();
var validator = GetValidator(type); // How?
var validatorDescriptor = validator.CreateDescriptor();
foreach (var key in model.Properties.Keys)
{
foreach (var propertyValidator in validatorDescriptor.GetValidatorsForMember(key))
{
// Add to model properties as in blog
}
}
}
}

Answer 1

I've created github project and nuget package based on Mujahid Daud Khan answer. I made redesign to support extensibility and supported other validators.
github: https://github.com/micro-elements/MicroElements.Swashbuckle.FluentValidation
nuget: https://www.nuget.org/packages/MicroElements.Swashbuckle.FluentValidation
Note: For WebApi see: https://github.com/micro-elements/MicroElements.Swashbuckle.FluentValidation.WebApi
Supported validators
INotNullValidator (NotNull)
INotEmptyValidator (NotEmpty)
ILengthValidator (Length, MinimumLength, MaximumLength, ExactLength)
IRegularExpressionValidator (Email, Matches)
IComparisonValidator (GreaterThan, GreaterThanOrEqual, LessThan, LessThanOrEqual)
IBetweenValidator (InclusiveBetween, ExclusiveBetween)
Usage
1. Reference packages in your web project:
<PackageReference Include="FluentValidation.AspNetCore" Version="7.5.2" />
<PackageReference Include="MicroElements.Swashbuckle.FluentValidation" Version="0.4.0" />
<PackageReference Include="Swashbuckle.AspNetCore" Version="2.3.0" />
2. Change Startup.cs
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services
.AddMvc()
// Adds fluent validators to Asp.net
.AddFluentValidation(fv => fv.RegisterValidatorsFromAssemblyContaining<CustomerValidator>());
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new Info { Title = "My API", Version = "v1" });
// Adds fluent validation rules to swagger
c.AddFluentValidationRules();
});
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
app
.UseMvc()
// Adds swagger
.UseSwagger();
// Adds swagger UI
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
});
}
Swagger Sample model and validator
public class Sample
{
public string PropertyWithNoRules { get; set; }
public string NotNull { get; set; }
public string NotEmpty { get; set; }
public string EmailAddress { get; set; }
public string RegexField { get; set; }
public int ValueInRange { get; set; }
public int ValueInRangeExclusive { get; set; }
}
public class SampleValidator : AbstractValidator<Sample>
{
public SampleValidator()
{
RuleFor(sample => sample.NotNull).NotNull();
RuleFor(sample => sample.NotEmpty).NotEmpty();
RuleFor(sample => sample.EmailAddress).EmailAddress();
RuleFor(sample => sample.RegexField).Matches(#"(\d{4})-(\d{2})-(\d{2})");
RuleFor(sample => sample.ValueInRange).GreaterThanOrEqualTo(5).LessThanOrEqualTo(10);
RuleFor(sample => sample.ValueInRangeExclusive).GreaterThan(5).LessThan(10);
}
}
Feel free to add issues!

Answer 2

After searching i have finally figured out that i needed to IValidationFactory for validator instance.
public class AddFluentValidationRules : ISchemaFilter
{
private readonly IValidatorFactory _factory;
/// <summary>
/// Default constructor with DI
/// </summary>
/// <param name="factory"></param>
public AddFluentValidationRules(IValidatorFactory factory)
{
_factory = factory;
}
/// <summary>
/// </summary>
/// <param name="model"></param>
/// <param name="context"></param>
public void Apply(Schema model, SchemaFilterContext context)
{
// use IoC or FluentValidatorFactory to get AbstractValidator<T> instance
var validator = _factory.GetValidator(context.SystemType);
if (validator == null) return;
if (model.Required == null)
model.Required = new List<string>();
var validatorDescriptor = validator.CreateDescriptor();
foreach (var key in model.Properties.Keys)
{
foreach (var propertyValidator in validatorDescriptor
.GetValidatorsForMember(ToPascalCase(key)))
{
if (propertyValidator is NotNullValidator
|| propertyValidator is NotEmptyValidator)
model.Required.Add(key);
if (propertyValidator is LengthValidator lengthValidator)
{
if (lengthValidator.Max > 0)
model.Properties[key].MaxLength = lengthValidator.Max;
model.Properties[key].MinLength = lengthValidator.Min;
}
if (propertyValidator is RegularExpressionValidator expressionValidator)
model.Properties[key].Pattern = expressionValidator.Expression;
// Add more validation properties here;
}
}
}
/// <summary>
/// To convert case as swagger may be using lower camel case
/// </summary>
/// <param name="inputString"></param>
/// <returns></returns>
private static string ToPascalCase(string inputString)
{
// If there are 0 or 1 characters, just return the string.
if (inputString == null) return null;
if (inputString.Length < 2) return inputString.ToUpper();
return inputString.Substring(0, 1).ToUpper() + inputString.Substring(1);
}
}
and add this class to swaggerGen options
options.SchemaFilter<AddFluentValidationRules>();

Answer 3

Install Nuget package: MicroElements.Swashbuckle.FluentValidation
Add to ConfigureServices:
services.AddFluentValidationRulesToSwagger();