What is Generic Repository?

A generic repository is a design pattern that provides a generic implementation for data access operations in a software application. It allows you to create a single repository class that can handle CRUD (Create, Read, Update, Delete) operations for multiple entity types in a type-safe and reusable manner.

The generic repository typically uses generics, a feature in programming languages like C#, to work with different types of entities without the need to create separate repository implementations for each entity. By using generics, you can define a common set of methods that can operate on any entity type, reducing code duplication and improving maintainability.

The key benefits of using a generic repository include:

1. Reusability: With a generic repository, you can create a single implementation that can be reused across multiple entities in your application. This saves development time and reduces code duplication.
2. Type Safety: The use of generics ensures that the repository methods operate on the correct entity types. This helps catch compile-time errors and provides a safer and more reliable approach to data access.
3. Simplified Codebase: By abstracting data access operations into a generic repository, you can simplify your codebase and make it more modular. This separation of concerns improves code organization and maintainability.
4. Flexibility: The generic repository allows you to add, update, delete, and retrieve entities without writing repetitive code for each entity type. It provides a consistent interface and reduces the effort required to perform basic data access operations.

Here’s a simplified example of a generic repository interface and implementation in C#:

public interface IRepository<TEntity> where TEntity : class
{
    TEntity GetById(int id);
    void Add(TEntity entity);
    void Update(TEntity entity);
    void Delete(TEntity entity);
}

public class Repository<TEntity> : IRepository<TEntity> where TEntity : class
{
    private DbContext _context;
    private DbSet<TEntity> _dbSet;

    public Repository(DbContext context)
    {
        _context = context;
        _dbSet = context.Set<TEntity>();
    }

    public TEntity GetById(int id)
    {
        return _dbSet.Find(id);
    }

    public void Add(TEntity entity)
    {
        _dbSet.Add(entity);
        _context.SaveChanges();
    }

    public void Update(TEntity entity)
    {
        _dbSet.Attach(entity);
        _context.Entry(entity).State = EntityState.Modified;
        _context.SaveChanges();
    }

    public void Delete(TEntity entity)
    {
        _dbSet.Remove(entity);
        _context.SaveChanges();
    }
}

In this example, the IRepository<TEntity> interface defines the common set of methods that the generic repository should implement. The Repository<TEntity> class is the concrete implementation of the generic repository. It uses a DbContext to interact with the underlying data source, and a DbSet<TEntity> to access the entities in the context.

By using this generic repository, you can create specific repository instances for different entity types by providing the appropriate entity class as the generic type parameter. This enables you to work with different entities using a consistent set of data access methods.