ReadonlyDbContextGenerator 0.2.4

ReadOnly DbContext Source Generator

Overview

The ReadOnlyDbContextGenerator is a C# source generator that creates read-only versions of EF Core DbContext and entities.

See CHANGELOG.md for release notes and recent changes.

How It Works

1. DbContext Analysis

   • Identifies classes inheriting from Microsoft.EntityFrameworkCore.DbContext.
   • Extracts the DbSet properties and their entity types.

2. Entity Processing

   • Analyzes the entity types referenced in the DbSet properties.
   • Converts their properties to init-only.
   • Modifies navigation properties to reference read-only entities or collections.

3. Entity Configuration

   • Identifies and processes IEntityTypeConfiguration implementations.
   • Generates read-only configuration classes for the entities.

4. Code Generation

   • Produces source files for:
     • Read-only DbContext.
     • Read-only entity classes.
     • Entity configuration classes.
     • IReadOnlyDbContext interface.

Usage

1. Add the source generator to your project:

   dotnet add package ReadonlyDbContextGenerator
   

2. Build your project. The generator will create source files for the read-only components.

3. Access the generated read-only DbContext and entities:

   var readOnlyDbContext = new ReadOnlyMyDbContext();
   

Read-only contract

Generated contexts inherit from the original DbContext type and throw NotSupportedException from every SaveChanges and SaveChangesAsync overload. Generated entities expose init accessors, and generated interfaces expose queryable sets rather than mutable DbSet members.

This is an application-level guard. EF Core bulk operations such as ExecuteUpdate and ExecuteDelete run directly against the database and do not call SaveChanges. Use database credentials with read-only permissions when writes must be prevented reliably.

The generator supports entities declared in the consuming project, navigation collections, owned types configured with OwnsOne, OwnsMany, or Owned, record entities, and IEntityTypeConfiguration<T> implementations. DbSet properties whose entity type is defined in another assembly are skipped with diagnostic RDCTX001.

Example

Input

DbContext

public class MyDbContext : DbContext
{
    public DbSet<User> Users { get; set; }
    public DbSet<Order> Orders { get; set; }
}

Entity

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Order> Orders { get; set; }
}

public class Order
{
    public int Id { get; set; }
    public string Product { get; set; }
    public User User { get; set; }
}

Generated Output

ReadOnlyMyDbContext

public partial class ReadOnlyMyDbContext : DbContext, IReadOnlyMyDbContext
{
    public DbSet<ReadOnlyUser> Users { get; }
    public DbSet<ReadOnlyOrder> Orders { get; }

    public sealed override int SaveChanges()
    {
        throw new NotSupportedException("Saving changes is not supported by a readonly db context.");
    }

    public sealed override int SaveChanges(bool acceptAllChangesOnSuccess)
    {
        throw new NotSupportedException("Saving changes is not supported by a readonly db context.");
    }

    IQueryable<ReadOnlyUser> IReadOnlyMyDbContext.Users => Users;
    IQueryable<ReadOnlyOrder> IReadOnlyMyDbContext.Orders => Orders;
    IQueryable<TEntity> IReadOnlyMyDbContext.Set<TEntity>()
        where TEntity : class => Set<TEntity>();
}

ReadOnlyUser

public class ReadOnlyUser
{
    public int Id { get; init; }
    public string Name { get; init; }
    public IReadOnlyCollection<ReadOnlyOrder> Orders { get; init; }
}

ReadOnlyOrder

public class ReadOnlyOrder
{
    public int Id { get; init; }
    public string Product { get; init; }
    public ReadOnlyUser User { get; init; }
}

IReadOnlyMyDbContext

public partial interface IReadOnlyMyDbContext : IDisposable, IAsyncDisposable
{
    IQueryable<ReadOnlyUser> Users { get; }
    IQueryable<ReadOnlyOrder> Orders { get; }
    IQueryable<TEntity> Set<TEntity>() where TEntity : class;
    DatabaseFacade Database { get; }
}

Contributing

Contributions are welcome! Please submit issues or pull requests on the ReadonlyDbContextGenerator.

We welcome ideas, bug reports, and feature suggestions from the community!