What Gets Generated

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For every [ValueObject] type, the generator emits a partial declaration alongside yours in a .g.cs file.

Class output

// Input
[ValueObject]
public partial class Money
{
    public decimal Amount { get; }
    public string Currency { get; }
}

// Generated (Money.g.cs)
sealed partial class Money : System.IEquatable<Money>
{
    public override bool Equals(object? obj) =>
        obj is Money other && Equals(other);

    public bool Equals(Money? other) =>
        other is not null &&
        Amount == other.Amount &&
        Currency == other.Currency;

    public override int GetHashCode() =>
        System.HashCode.Combine(Amount, Currency);

    public static bool operator ==(Money? left, Money? right) =>
        left is null ? right is null : left.Equals(right);

    public static bool operator !=(Money? left, Money? right) =>
        !(left == right);

    public override string ToString() =>
        $"Money {{ Amount = {Amount}, Currency = {Currency} }}";
}

Struct output

// Input
[ValueObject]
public partial struct CustomerId
{
    public int Value { get; }
}

// Generated
readonly partial struct CustomerId : System.IEquatable<CustomerId>
{
    public override bool Equals(object? obj) =>
        obj is CustomerId other && Equals(other);

    public bool Equals(CustomerId other) =>    // no nullable — structs can't be null
        Value == other.Value;

    public override int GetHashCode() =>
        System.HashCode.Combine(Value);

    public static bool operator ==(CustomerId left, CustomerId right) =>
        left.Equals(right);                    // no null guard needed

    public static bool operator !=(CustomerId left, CustomerId right) =>
        !left.Equals(right);

    public override string ToString() =>
        $"CustomerId {{ Value = {Value} }}";
}

Hash code strategy

Number of properties	Strategy
0	return 0;
1–8	System.HashCode.Combine(p1, p2, ...)
9+	var hc = new System.HashCode(); hc.Add(p1); ... return hc.ToHashCode();

Type modifiers

Type	Generated modifier
partial class	sealed partial class
partial struct	readonly partial struct
partial struct with ForceClass = true	sealed partial class

Classes are sealed to prevent subclasses from accidentally inheriting equality semantics and to allow the JIT to devirtualize Equals calls.

Structs are readonly because mutable value-type equality is a known footgun in C#.