Repository.cs

using LibraryManagement.Data.Interfaces;
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace LibraryManagement.Data.Repository
{
    // This class abstracts out the most common basic operations for
    // interaction with the database entities: Creating, Reading, Updating, Deleting (CRUD).
    public abstract class Repository<T> : IRepository<T> where T : class
    {        
        // This variable references the database context.
        // It is used for Entity framework operations, encapsulated further within the code
        protected readonly LibraryDbContext _context;
        public Repository(LibraryDbContext context)
        {
            _context = context;
        }
        
        // Just to make is shorter and clearer
        protected void Save() => _context.SaveChanges();

        // Abstact Creation operation basically abstracts out 
        // the simplest Entity framework scenario
        // Expand it within the definitions of inherited repos to
        // add more specific functionality, such as
        // more complex check-ins, etc.
        public void Create(T entity)
        {
            _context.Add(entity);

            Save();
        }
        
        // Common method for entity removal
        public virtual void Delete(T entity)
        {
            _context.Remove(entity);

            Save();
        }
        
        // Common method for entities reading from the database.
        public IEnumerable<T> GetAll()
        {
            return _context.Set<T>();
        }
        
        // Common method for entity retreival
        public T GetById(int id)
        {
            return _context.Set<T>().Find(id);
        }
        
        // Common method for entity updates
        public void Update(T entity)
        {
            _context.Entry(entity).State = EntityState.Modified;

            Save();
        }
        
        // Common method for entity retreival based on a predicate
        public IEnumerable<T> Find(Func<T, bool> predicate)
        {
            return _context.Set<T>().Where(predicate);
        }
        
        // Common method for getting number of entities
        public int Count(Func<T, Boolean> predicate)
        {
            return _context.Set<T>().Where(predicate).Count();
        }
        
        // Common method for checking whether any entity satisfying the given
        // condition exist
        public bool Any(Func<T, bool> predicate)
        {
            return _context.Set<T>().Any(predicate);
        }
        
        // Common method for checking whether the SQL table is not empty
        public bool Any()
        {
            return _context.Set<T>().Any();
        }
    }
}