Csharp 是否可以为此限制泛型参数类型

Short version

如何强制BaseClass的TModel泛型参数与派生自它的类的类型相同？

public class BaseClass<TModel, TValidator> where TValidator : IValidator<TModel> { }

public class Person : BaseClass<Person, PersonValidator> { }

在本例中，如何强制BaseClass的TModel为Person类型而不是其他类型？

这是无效的语法，但这是我想象的:

public class BaseClass<TValidator> where TValidator : IValidator<this> { }

public class Person : BaseClass<PersonValidator> { }

这是否有可能，或者我应该使用完全不同的解决方案来实现这一点？

Long version

我试图将一些验证逻辑提取到基类中，但我不知道如何约束泛型类型，因此生成的基类是完全可靠的.

下面是一个没有基类的所有验证逻辑的示例.我使用FluentValidation来验证对象，并通过IDataErrorInfo接口公开验证结果，以便WPF UI可以使用它.

Original solution

public class User : IDataErrorInfo 
{
    private readonly IValidator<Person> _validator = new();

    public string Username { get; set; }
    public string Password { get; set; }

    private string ValidateAndGetErrorForProperty(string propertyName)
    {
        var result = _validator.Validate(this);

        if (result.IsValid)
        {
            return string.Empty;
        }

        return result.Errors.FirstOrDefault(a => a.PropertyName == propertyName)?.ErrorMessage ?? string.Empty;
    }

    //IDataErrorInfo implementation
    public string Error => string.Empty;
    public string this[string columnName] => ValidateAndGetErrorForProperty(columnName);
}

public class UserValidator : AbstractValidator<User>
{
    public UserValidator()
    {
        RuleFor(a => a.Username)
            .EmailAddress();

        RuleFor(a => a.Password)
            .MinimumLength(12);
    }
}

Validation implementation separated into a base class

我想将验证逻辑和IDataErrorInfo实现分离到一个基类中，这样就不必在每个模型类中重复这个样板.这是我的.

public abstract class ValidationBase<TModel, TValidator> : IDataErrorInfo where TValidator : IValidator<TModel>, new()
{
    private readonly TValidator _validator;

    public ValidationBase()
    {
        _validator = Activator.CreateInstance<TValidator>();
    }

    private string ValidateAndGetErrorForProperty(string propertyName)
    {
        //I have to check if this is of type TModel since the TModel isn't constraint to this
        if (this is not TModel model)
        {
            throw new InvalidOperationException($"Instance is not of the supported type: {typeof(TModel)}. Type of {GetType()} found instead");
        }

        var result = _validator.Validate(model);

        if (result.IsValid)
        {
            return string.Empty;
        }

        return result.Errors.FirstOrDefault(a => a.PropertyName == propertyName)?.ErrorMessage ?? string.Empty;
    }

    //IDataErrorInfo implementation
    public string Error => string.Empty;
    public string this[string columnName] => ValidateAndGetErrorForProperty(columnName);
}

下面是我如何使用它:

public class User : ValidationBase<User, UserValidator>
{
    public string Username { get; set; }
    public string Password { get; set; }
}

The problem

此解决方案的问题是，您可以编写以下无效代码:

public class InvalidClass : ValidationBase<User, UserValidator>
{
    
}