EF Core Web API：外键验证

Question

假设我有这些课程：

public class User
{
    public int? Id { get; set; }
    ...
}

public class Wallet
{
    public int? Id { get; set; }
    public string Title {get; set;}
    public User Owner { get; set; }
    ...
}

public class WalletCreationDTO 
{
    [Required]
    public string Title {get; set;}
    [Required]
    public int OwnerId { get; set; }
}

[HttpPost]
public async Task<ActionResult> CreateWallet(WalletCreationDto walletDTO) {...}

我必须像这样向前端报告任何错误的参数：

{  
    "errors": {  
        "ownerId": "User by Id does not exist",  
        "title": "Must not exceed 8 characters"  
    }  
}

如何验证 OwnerId？

• 手动查询数据库似乎无效
• 默认的 ASP.NET Core 验证似乎没有任何与数据库访问相关的注释

Answer 1

我最终使用了流畅的验证as suggested。这不是最有效的方法，但我正在权衡漂亮的错误和简单的代码。

public class WalletCreateDTO
{
    [Required]
    [MaxLength(20)]
    public string Title { get; set; }

    [Required]
    public int OwnerId { get; set; }

    [Required]
    public string CurrencyCode { get; set; }
}

public class WalletCreateDTOValidator : AbstractValidator<WalletCreateDTO>
{
    public WalletCreateDTOValidator(Data.Database database)
    {
        this.RuleFor(w => w.OwnerId)
            .Must(ownerId => database.Users.Any(user => user.Id == ownerId))
            .WithMessage("User does not exist");
        this.RuleFor(w=> w.CurrencyCode)
            .Must(currencyCode => database.Currencies.Any(currency => currency.Code == currencyCode))
            .WithMessage("Currency does not exist");
    }
}

--- To anyone reading this in the future ---

NuGet 包：FluentValidation.AspNetCore

配置：

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers()
        .AddFluentValidation(config =>
        {
            config.RegisterValidatorsFromAssembly(typeof(WalletCreateDTO).Assembly);
        });
}

注意：这似乎注册了程序集中的所有验证器。比如我所有的DTO都在Api.Dtos目录/命名空间里，好像都注册了，很方便。

此外，还有大摇大摆的集成：MicroElements.Swashbuckle.FluentValidation

Answer 2

您可以在简单模式下使用它。

        [HttpPost]
        public async Task<ActionResult> CreateWallet(WalletCreationDto walletDTO)
        {
            bool isValidOwnerId = /*validationLogic => can use service or Repository or etc... */

            if (isValidOwnerId == false)
                ModelState.AddModelError("OwnerId", "errorMessage");


            if (ModelState.IsValid)
            {
                //CreateWallet Loigc......
            }

            //we can get all errors from ModelState
            List<ModelError> allErrors = ModelState.Values.SelectMany(v => v.Errors).ToList();

            /*
             return .... 
            */
        }

我还建议您阅读以下两个链接。

IValidatableObject

fluentvalidation：用于构建强类型验证规则的流行 .NET 库。