ASP.NET Core Web API - 如何使用 Fluent Validation 实现可选验证

Question

I have this validator using Fluent Validation in ASP.NET Core-6 Web API:我有这个验证器在 ASP.NET Core-6 Web API 中使用 Fluent Validation：

public TransactionValidator()
{
    RuleFor(p => p.Token)
        .Cascade(CascadeMode.StopOnFirstFailure);
}

Token should either be null, or it has input value of exactly 6 lengths.令牌应该是 null，或者它的输入值正好是 6 个长度。

How do I get this done?我如何完成这项工作？

Answer 1

Fluent validation supports predicate validator via Must : Fluent 验证通过Must支持谓词验证器：

RuleFor(p => p.Token)
    .Cascade(CascadeMode.Stop)
    .Must(s => s == null || s.Length == 6);

Or the same can be achieved with conditions :或者可以通过条件实现相同的目的：

RuleFor(p => p.Token)
    .Cascade(CascadeMode.Stop)
    .Length(6)
    .When(c => c.Token != null);