Conditional & RuleSet

When — Conditional Validation

Rules inside b.When() only fire when the condition is true:

public void Configure(IValidationBuilder<ShippingRequest> b)
{
    b.When(x => x.RequiresShipping, then =>
    {
        then.Property(x => x.ShippingAddress).Required();
        then.Property(x => x.PostalCode).Required().Match(@"^\d{5}$");
        then.Rule(x => !string.IsNullOrEmpty(x.City), "City is required for shipping");
    });
}

When RequiresShipping == false → all inner rules skipped.

Unless — Inverse Conditional

Rules inside b.Unless() fire when the condition is false:

public void Configure(IValidationBuilder<PaymentRequest> b)
{
    b.Unless(x => x.IsFreeOrder, then =>
    {
        then.Property(x => x.CardNumber).Required().CreditCard();
        then.Property(x => x.ExpiryDate).Required();
    });
}

IsFreeOrder == true → card rules skipped. IsFreeOrder == false → card required.

RuleSet — Named Groups

Group rules and validate selectively:

[ZValidate]
public partial class UserDto : IValidationConfigurator<UserDto>
{
    [ZRequired] public string Name { get; set; } = "";
    [ZRequired] [ZEmail] public string Email { get; set; } = "";
    public string Password { get; set; } = "";
    public int Id { get; set; }

    public void Configure(IValidationBuilder<UserDto> b)
    {
        b.RuleSet("Create", set =>
        {
            set.Rule(x => !string.IsNullOrEmpty(x.Password), "Password required for creation");
            set.Rule(x => x.Password.Length >= 8, "Password must be at least 8 characters");
        });

        b.RuleSet("Update", set =>
        {
            set.Rule(x => x.Id > 0, "Id required for update");
        });
    }
}

Usage:

// Validate ALL rules (attributes + base rules + all rulesets):
var result = dto.Validate();

// Validate only "Create" ruleset (+ base attribute/expression rules):
var result = dto.Validate(null, "Create");

// Validate only "Update" ruleset:
var result = dto.Validate(null, "Update");

// Multiple sets:
var result = dto.Validate(null, "Create", "Update");

Base rules (attributes + b.Rule() outside any set) always run. RuleSets are additive.

When to use RuleSet

Scenario	Approach
Same DTO for create + update	b.RuleSet("Create", ...) for password, b.RuleSet("Update", ...) for Id
Multi-step wizard	One set per step: “Step1”, “Step2”, “Step3”
Admin vs User validation	b.RuleSet("Admin", ...) with stricter rules

Combining When + RuleSet

public void Configure(IValidationBuilder<OrderDto> b)
{
    b.RuleSet("Shipping", set =>
    {
        set.When(x => x.DeliveryMethod == "express", then =>
        {
            then.Rule(x => x.ExpressAddress != null, "Express address required");
        });
    });
}

Validates only when: you request “Shipping” set AND DeliveryMethod == "express".