GenericRepo.cs

public interface IRepository<TEntity> where TEntity : class
{
    IEnumerable<TEntity> Get(
        Expression<Func<TEntity, bool>> filter = null,
        Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
        string includeProperties = "");

    TEntity GetById(object id);
    void AddOrUpdate(TEntity entity);
    void Delete(object id);
    void Delete(TEntity entityToDelete);
    void Update(TEntity entityToUpdate);
}

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

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

    public virtual IEnumerable<TEntity> Get(
        Expression<Func<TEntity, bool>> filter = null,
        Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
        string includeProperties = "")
    {
        IQueryable<TEntity> query = _dbSet;

        if (filter != null)
        {
            query = query.Where(filter);
        }

        foreach (string includeProperty in includeProperties.Split
            (new[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
        {
            query = query.Include(includeProperty);
        }

        if (orderBy != null)
        {
            return orderBy(query).ToList();
        }
        else
        {
            return query.ToList();
        }
    }

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

    public virtual void AddOrUpdate(TEntity entity)
    {
        _dbSet.AddOrUpdate(new []{entity});
    }

    public virtual void Delete(object id)
    {
        TEntity entityToDelete = _dbSet.Find(id);
        Delete(entityToDelete);
    }

    public virtual void Delete(TEntity entityToDelete)
    {
        if (_context.Entry(entityToDelete).State == EntityState.Detached)
        {
            _dbSet.Attach(entityToDelete);
        }
        _dbSet.Remove(entityToDelete);
    }

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