Value Type Generators

Installation

dotnet add package ValueTypeGenerators

How to generate

[ValueType(Type = TypeOfValue.Int32)]
public readonly partial struct Int32Id;

[ValueType(Type = TypeOfValue.Int32)]
public readonly partial struct PersonId;

[ValueType(Type = TypeOfValue.Int32)]
public readonly partial struct StudentId;

[ValueType(Type = TypeOfValue.Int32)]
public readonly partial struct ManagerId;

[ValueType(Type = TypeOfValue.Int64)]
public readonly partial struct Int64Id;

[ValueType(Type = TypeOfValue.Int64)]
public readonly partial struct TimestampId;

[ValueType(Type = TypeOfValue.Guid)]
public readonly partial struct GloballyUniqueId;

[ValueType(Type = TypeOfValue.Guid)]
public readonly partial struct ProductId;

[ValueType(Type = TypeOfValue.Guid)]
public readonly partial struct SubscriptionId;

[ValueType(Type = TypeOfValue.Guid)]
public readonly partial struct MarketId;

The property Type of ValueType attribute has a default value of TypeOfValue.Guid, so the ProductId above and other Guid-based types could be defined as:

[ValueType]
public readonly partial struct ProductId;

What's Generated

Below is the simplified version of what's generated.

// Value Type
// There is no Value property; instead, casting operators should be used
[StructLayout(LayoutKind.Explicit)]
struct ProductId {
    [FieldOffset(0)]
    private readonly Guid _value;
    
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static explicit operator ProductId(Guid g) => Unsafe.As<Guid, ProductId>(ref g);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static explicit operator Guid(ProductId id) => id._value;
}

// System.Text.Json Converter
class ProductIdJsonConverter : JsonConverter<ProductId>;

// Entity Framework Core Value Comparer
class ProductIdValueComparer : ValueComparer<ProductId>;

// Entity Framework Core Value Converter
class ProductIdValueConverter : ValueConverter<ProductId, Guid>;

// Entity Framework Core Conventions
static class ValueTypeConventionExtensions {
    public static void AddValueTypeConversions(this ModelConfigurationBuilder config);
}

Usage

As Guid

[ValueType]
readonly partial struct ProductId;

record Product {
    public ProductId Id { get; }
}

Casting is the only way to get the value.

var productId = (ProductId)Guid.NewGuid(); // equivalent to the generated method ProductId.NewProductId()
var productIdAsGuid = (Guid)productId;

As int

[ValueType(Type = TypeOfValue.Int32)]
readonly partial struct ProductId;

Again, casting is the only way to get the value.

var productId = (ProductId)123;
var productIdAsInt = (int)productId;

Implicit cast operators

[ValueType(CastOperator = CastOperator.Implicit)]
readonly partial struct ProductId;

Once again, casting is the only way to get the value, but this time it's implicit.

ProductId productId = Guid.NewGuid(); // equivalent to ProductId.NewProductId()
Guid productIdAsGuid = productId;

Entity Framework Core

class DeliveryDbContext : DbContext {
    protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder) {
        base.ConfigureConventions(configurationBuilder);

        configurationBuilder.AddValueTypeConversions();
    }
    
    protected override void OnModelCreating(ModelBuilder builder) {
        base.OnModelCreating(builder);

        builder.Entity<Product>(static cfg => {
            cfg.HasKey(static x => x.Id);
            cfg.Property(static x => x.Id).ValueGeneratedOnAdd();
        });
    }
}

ASP.NET Core

app.MapGet("/products/{id}", static ([FromRoute] ProductId id) => {
    // ...
});

app.MapGet("/people/{id}", static ([FromRoute] PersonId id) => {
    // ...
});

app.MapGet("/time/{id}", static ([FromRoute] TimestampId id) => {
    // ...
});