Lots of changes to get code ready to add library.

API/Data/LibraryRepository.cs

@@ -0,0 +1,45 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using API.DTOs;
+using API.Entities;
+using API.Interfaces;
+using AutoMapper;
+using AutoMapper.QueryableExtensions;
+using Microsoft.EntityFrameworkCore;
+
+namespace API.Data
+{
+    public class LibraryRepository : ILibraryRepository
+    {
+        private readonly DataContext _context;
+        private readonly IMapper _mapper;
+
+        public LibraryRepository(DataContext context, IMapper mapper)
+        {
+            _context = context;
+            _mapper = mapper;
+        }
+
+        public void Update(Library library)
+        {
+            _context.Entry(library).State = EntityState.Modified;
+        }
+
+        public async Task<bool> SaveAllAsync()
+        {
+            return await _context.SaveChangesAsync() > 0;
+        }
+
+        public async Task<IEnumerable<LibraryDto>> GetLibrariesAsync()
+        {
+            return await _context.Library
+                .Include(f => f.Folders)
+                .ProjectTo<LibraryDto>(_mapper.ConfigurationProvider).ToListAsync();
+        }
+
+        public async Task<bool> LibraryExists(string libraryName)
+        {
+            return await _context.Library.AnyAsync(x => x.Name == libraryName);
+        }
+    }
+}