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Comparison & Boolean Methods

This page documents all boolean checks, null checks, equality comparisons, type checks, and cross-field comparisons available on ValiFlow<T>.

Examples: ValiFlow · Evaluators

Boolean Checks​

IsTrue(selector)​

The selected property must evaluate to true.

var rule = new ValiFlow<User>()
    .IsTrue(u => u.IsActive);

IsFalse(selector)​

The selected property must evaluate to false.

var rule = new ValiFlow<User>()
    .IsFalse(u => u.IsDeleted);

Null Checks​

NotNull(selector)​

The selected member must not be null. Throws if the selector always produces a non-nullable value type.

var rule = new ValiFlow<Order>()
    .NotNull(o => o.CustomerId);

IsNotNull(selector)​

Alias for NotNull. Prefer this name for consistency with the Is* naming convention.

var rule = new ValiFlow<Product>()
    .IsNotNull(p => p.Name);

Null(selector)​

The selected member must be null.

var rule = new ValiFlow<User>()
    .Null(u => u.DeletedAt);

IsNull(selector)​

Alias for Null.

var rule = new ValiFlow<Order>()
    .IsNull(o => o.CancelledAt);

Equality​

EqualTo(selector, value)​

The selected property must equal value. TValue must implement IEquatable<TValue>.

var rule = new ValiFlow<Order>()
    .EqualTo(o => o.Status, "Active");

NotEqualTo(selector, value)​

The selected property must not equal value.

var rule = new ValiFlow<Order>()
    .NotEqualTo(o => o.Status, "Cancelled");

Type Checks​

IsInEnum(selector)​

The selected value must be a defined member of its enum type. This check uses Enum.IsDefined and is evaluated in memory.

Note: In-memory only. This method is not translatable to SQL by EF Core. Use ValiFlow<T> (not ValiFlowQuery<T>) when this condition is required.

var rule = new ValiFlow<Order>()
    .IsInEnum(o => o.PaymentMethod);

IsDefault(selector)​

The selected value must equal default(TValue) — i.e., null for reference types, 0 for numeric types, DateTime.MinValue for DateTime, etc.

Note: In-memory only. Not translatable to SQL by EF Core.

var rule = new ValiFlow<Booking>()
    .IsDefault(b => b.CheckOutDate); // true when CheckOutDate == default(DateTime)

IsNotDefault(selector)​

The selected value must not equal default(TValue).

Note: In-memory only. Not translatable to SQL by EF Core.

var rule = new ValiFlow<Booking>()
    .IsNotDefault(b => b.Id); // ensures Id has been assigned

Cross-Field Comparisons​

These methods compare two properties of the same entity against each other. The selector type TValue must implement IComparable<TValue>, which includes DateTime, decimal, int, string, DateOnly, TimeOnly, DateTimeOffset, and any other comparable type.

GreaterThan(leftSelector, rightSelector)​

left > right — the left property must be strictly greater than the right property.

var rule = new ValiFlow<Booking>()
    .GreaterThan(b => b.CheckOut, b => b.CheckIn);

GreaterThanOrEqualTo(leftSelector, rightSelector)​

left >= right.

var rule = new ValiFlow<Product>()
    .GreaterThanOrEqualTo(p => p.MaxPrice, p => p.MinPrice);

LessThan(leftSelector, rightSelector)​

left < right.

var rule = new ValiFlow<Order>()
    .LessThan(o => o.DiscountedPrice, o => o.OriginalPrice);

LessThanOrEqualTo(leftSelector, rightSelector)​

left <= right.

var rule = new ValiFlow<Warehouse>()
    .LessThanOrEqualTo(w => w.CurrentStock, w => w.Capacity);

Practical Example​

The following rule combines boolean, null, equality, type, and cross-field comparisons to validate a Booking entity:

var rule = new ValiFlow<Booking>()
    // Id must have been assigned (not default)
    .IsNotDefault(b => b.Id)
    // Guest name must not be null
    .IsNotNull(b => b.GuestName)
    // Only confirmed bookings are accepted
    .EqualTo(b => b.Status, BookingStatus.Confirmed)
    // PaymentMethod must be a valid enum value
    .IsInEnum(b => b.PaymentMethod)
    // Booking must not be cancelled
    .IsFalse(b => b.IsCancelled)
    // Check-out must come after check-in
    .GreaterThan(b => b.CheckOut, b => b.CheckIn);

var result = rule.Validate(booking);
if (!result.IsValid)
    Console.WriteLine($"Booking invalid: {result.ErrorMessage}");

Note: IsNotDefault and IsInEnum are in-memory only. If you pass this rule's Build() output to an EF Core query, those conditions will throw a translation exception. In that scenario, evaluate them separately in memory after the database query, or replace them with EF Core-translatable equivalents.

Mini Examples​

1) Soft-delete + status check​

var rule = new ValiFlow<Order>()
    .IsFalse(o => o.IsDeleted)
    .EqualTo(o => o.Status, OrderStatus.Confirmed);

2) Cross-field date guard​

var rule = new ValiFlow<Booking>()
    .IsNotNull(b => b.CheckIn)
    .IsNotNull(b => b.CheckOut)
    .GreaterThan(b => b.CheckOut, b => b.CheckIn);