為了驗證api post上來的資料的有效性，我們可以引入FluentValidation(詳見https://fluentvalidation.net)。在asp.net mvc中，使用的是模型驗證，通過在實體類上新增特性達到驗證效果。

　　FluentValidation的原理是通過實現AbstractValidator<T>來實現對T實體類的驗證，通過不同折Rule來驗證T中的屬性（更多驗證規則 ，參見官網），見如下實現：

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Tel { get; set; }
    public string Email { get; set; }
    public DateTime Birthday { get; set; }
    public string IDCard { get; set; }
    public PersonAddress Address { get; set; }
}
public class PersonAddress
{
    public string Country { get; set; }
    public string Province { get; set; }
    public string City { get; set; }
    public string County { get; set; }
    public string Address { get; set; }
    public string Postcode { get; set; }
}

/// <summary>
/// Person驗證
/// </summary>
public class PersonValidator : AbstractValidator<Person>
{
    public PersonValidator(IPersonService personService)
    {
        RuleFor(p => p.Name).NotNull().NotEmpty();
        RuleFor(p => p.Email).NotNull().EmailAddress();
        RuleFor(p => p.Birthday).NotNull();
        RuleFor(p => p.IDCard)
            .NotNull()
            .NotEmpty()
            .Length(18)
            .When(p => (DateTime.Now > p.Birthday.AddYears(1)))
            .WithMessage(p => $"出生日期為{p.Birthday}，現在時間為{DateTime.Now},大於一歲，CardID值必填！");
        RuleFor(p => p.Tel).NotNull().Matches(@"^(\d{3,4}-)?\d{6,8}$|^[1]+[3,4,5,8]+\d{9}$").WithMessage("電話格式為：0000-0000000或13000000000");
        RuleFor(p => p.Address).NotNull();
        RuleFor(p => p.Address).SetValidator(new PersonAddressValidator());
        //通過呼叫外部方法來驗證
        RuleFor(p => p.Id).Must(id => personService.IsExist(id)).WithMessage(p => $"不存在id={p.Id}的使用者");
    }
}
/// <summary>
/// Person Address驗證
/// </summary>
public class PersonAddressValidator : AbstractValidator<PersonAddress>
{
    public PersonAddressValidator()
    {
        RuleFor(a => a.Country).NotNull().NotEmpty();
        RuleFor(a => a.Province).NotNull().NotEmpty();
        RuleFor(a => a.City).NotNull().NotEmpty();
        RuleFor(a => a.County).NotNull().NotEmpty();
        RuleFor(a => a.Address).NotNull().NotEmpty();
        RuleFor(a => a.Postcode).NotNull().NotEmpty().Length(6);
    }
}
 

　　在mini api引入FluentValidation也很簡單，可以通過注入IValidator<T>實現，也可以注放AddFluentValidation，用IValidatorFactory來獲取Validator來實現驗證，程式碼如下：

using FluentValidation;
using FluentValidation.AspNetCore;
using System.Text;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddFluentValidation();
builder.Services.AddScoped<IValidator<Person>, PersonValidator>();
builder.Services.AddScoped<IPersonService, PersonService>();
var app = builder.Build();


app.MapPost("/person", async (IValidator<Person> validator, Person person) =>
 {
     var result = await validator.ValidateAsync(person);
     if (!result.IsValid)
     {
         var errors = new StringBuilder();
         foreach (var valid in result.Errors)
         {
             errors.AppendLine(valid.ErrorMessage);
         }
         return errors.ToString();
     }
     return "OK";
 });


app.MapPost("/person1", async (IValidatorFactory validatorFactory, Person person) =>
{
    var result = await validatorFactory.GetValidator<Person>().ValidateAsync(person);
    if (!result.IsValid)
    {
        var errors = new StringBuilder();
        foreach (var valid in result.Errors)
        {
            errors.AppendLine(valid.ErrorMessage);
        }
        return errors.ToString();
    }
    return "OK";
});

app.MapPost("/person2", async (IValidatorFactory validatorFactory, Person person) =>
{
    var result = await validatorFactory.GetValidator(typeof(Person)).ValidateAsync(new ValidationContext<Person>(person));
    if (!result.IsValid)
    {
        var errors = new StringBuilder();
        foreach (var valid in result.Errors)
        {
            errors.AppendLine(valid.ErrorMessage);
        }
        return errors.ToString();
    }
    return "OK";
});


app.Run();



public interface IPersonService
{
    public bool IsExist(int id);
}
public class PersonService : IPersonService
{
    public bool IsExist(int id)
    {
        if (DateTime.Now.Second % 2 == 0)
        {
            return false;
        }
        else
        {
            return true;
        }
    }
}