API Reference: D20Tek.LowDb.Repositories

The D20Tek.LowDb.Repositories package adds a repository abstraction over a LowDb database. It exposes CRUD, range, querying, existence checks, and batched save operations, with every method returning a Result<T> (from D20Tek.Functional) so callers can handle success and failure without exceptions.

Table of Contents

DbDocument

namespace D20Tek.LowDb.Repositories;

public abstract class DbDocument

The base type for LowDb database documents used with the repository pattern. A document typically exposes one or more HashSet<T> collections that a repository projects to and manages as entity sets.

Example

public class TasksDocument : DbDocument
{
	public HashSet<TaskEntity> Tasks { get; set; } = [];
}

IRepository<TEntity>

namespace D20Tek.LowDb.Repositories;

public interface IRepository<TEntity> where TEntity : class

Defines a synchronous repository abstraction over a LowDb document that exposes CRUD, range, query, and change-persistence operations for a single entity type.

Members

Member Description
Result<IEnumerable<TEntity>> GetAll() Gets all entities in the underlying entity set.
Result<TEntity> GetById<TProperty>(Expression<Func<TEntity, TProperty>> idSelector, TProperty id) Gets a single entity by matching the value of its identifier property. Returns a not-found failure when no match exists.
Result<IEnumerable<TEntity>> Find(Expression<Func<TEntity, bool>> predicate) Finds all entities that satisfy the specified predicate.
Result<bool> Exists(Expression<Func<TEntity, bool>> predicate) Determines whether any entity satisfies the specified predicate.
Result<TEntity> Add(TEntity entity) Adds an entity to the entity set. Returns a conflict failure when it already exists.
Result<IEnumerable<TEntity>> AddRange(IEnumerable<TEntity> entities) Adds multiple entities. Returns a conflict failure on the first entity that cannot be added.
Result<TEntity> Remove(TEntity entity) Removes an entity from the entity set. Returns a failure when it could not be removed.
Result<IEnumerable<TEntity>> RemoveRange(IEnumerable<TEntity> entities) Removes multiple entities. Returns a failure on the first entity that cannot be removed.
Result<TEntity> Update(TEntity entity) Marks an entity as updated. Entities are held by reference, so in-place mutations are already reflected in the entity set; call SaveChanges to persist them.
Result<bool> SaveChanges() Persists all pending changes to the underlying LowDb document. Multiple batched changes can be applied before a single save.

IRepositoryAsync<TEntity>

namespace D20Tek.LowDb.Repositories;

public interface IRepositoryAsync<TEntity> where TEntity : class

The asynchronous counterpart to IRepository<TEntity>. Every member mirrors its synchronous equivalent, accepts a CancellationToken token = default, and returns a Task<Result<T>>.

Members

Member Description
Task<Result<IEnumerable<TEntity>>> GetAllAsync(CancellationToken token = default) Gets all entities in the underlying entity set.
Task<Result<TEntity>> GetByIdAsync<TProperty>(Expression<Func<TEntity, TProperty>> idSelector, TProperty id, CancellationToken token = default) Gets a single entity by matching the value of its identifier property.
Task<Result<IEnumerable<TEntity>>> FindAsync(Expression<Func<TEntity, bool>> predicate, CancellationToken token = default) Finds all entities that satisfy the specified predicate.
Task<Result<bool>> ExistsAsync(Expression<Func<TEntity, bool>> predicate, CancellationToken token = default) Determines whether any entity satisfies the specified predicate.
Task<Result<TEntity>> AddAsync(TEntity entity, CancellationToken token = default) Adds an entity to the entity set.
Task<Result<IEnumerable<TEntity>>> AddRangeAsync(IEnumerable<TEntity> entities, CancellationToken token = default) Adds multiple entities to the entity set.
Task<Result<TEntity>> RemoveAsync(TEntity entity, CancellationToken token = default) Removes an entity from the entity set.
Task<Result<IEnumerable<TEntity>>> RemoveRangeAsync(IEnumerable<TEntity> entities, CancellationToken token = default) Removes multiple entities from the entity set.
Task<Result<TEntity>> UpdateAsync(TEntity entity, CancellationToken token = default) Marks an entity as updated; call SaveChangesAsync to persist in-place mutations.
Task<Result<bool>> SaveChangesAsync(CancellationToken token = default) Persists all pending changes to the underlying LowDb document.

LowDbRepository<TEntity, TDocument>

namespace D20Tek.LowDb.Repositories;

public class LowDbRepository<TEntity, TDocument>(
	LowDb<TDocument> db,
	Expression<Func<TDocument, HashSet<TEntity>>> setSelector) : IRepository<TEntity>
	where TEntity : class
	where TDocument : DbDocument, new()

A synchronous IRepository<TEntity> implementation that manages a HashSet<TEntity> stored within a LowDb document. Read operations query the in-memory document (via LowDb<TDocument>.Get()) while SaveChanges persists the current state through the underlying database (LowDb<TDocument>.Write()).

Constructor

Parameter Type Description
db LowDb<TDocument> The LowDb database that stores the document.
setSelector Expression<Func<TDocument, HashSet<TEntity>>> An expression that selects the entity set within the document.

Example

public interface ITasksRepository : IRepository<TaskEntity>;

public class TasksRepository(LowDb<TasksDocument> db)
	: LowDbRepository<TaskEntity, TasksDocument>(db, x => x.Tasks), ITasksRepository
{
}

var result = repository.Add(new TaskEntity { Id = 1, Name = "Write docs" });
repository.SaveChanges();

LowDbAsyncRepository<TEntity, TDocument>

namespace D20Tek.LowDb.Repositories;

public class LowDbAsyncRepository<TEntity, TDocument>(
	LowDbAsync<TDocument> db,
	Expression<Func<TDocument, HashSet<TEntity>>> setSelector) : IRepositoryAsync<TEntity>
	where TEntity : class
	where TDocument : DbDocument, new()

The asynchronous counterpart to LowDbRepository<TEntity, TDocument>, backed by LowDbAsync<TDocument>.

Constructor

Parameter Type Description
db LowDbAsync<TDocument> The asynchronous LowDb database that stores the document.
setSelector Expression<Func<TDocument, HashSet<TEntity>>> An expression that selects the entity set within the document.

Example

public interface ITasksRepository : IRepositoryAsync<TaskEntity>;

public class TasksRepository(LowDbAsync<TasksDocument> db)
	: LowDbAsyncRepository<TaskEntity, TasksDocument>(db, x => x.Tasks), ITasksRepository
{
}

await repository.AddAsync(new TaskEntity { Id = 1, Name = "Write docs" });
await repository.AddAsync(new TaskEntity { Id = 2, Name = "Ship release" });
var result = await repository.SaveChangesAsync();

Errors

namespace D20Tek.LowDb.Repositories;

internal static class Errors

Internal helper methods that build standardized Result<T> failures used throughout the repository implementations:

Member Description
Result<T> NotFoundError<T>(object id) Builds a not-found failure for a missing entity identifier.
Result<T> AddFailedError<T>(object entity) Builds a conflict failure when an entity cannot be added (for example, a duplicate in the HashSet<T>).
Result<T> RemoveFailedError<T>(object entity) Builds a failure when an entity cannot be removed.

This type is internal and not part of the package's public API; it is documented here for completeness when reading the repository source.

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