EF - Entity Graph

CSharp · Console

/Program.cs

// @nuget: EntityFramework

using System;
using System.Data.Entity;
using System.Linq;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;


public class Program
{
	public static void Main()
	{
		InsertData();
		
		Category programmingCat;
		
		using(var context = new BookStore())
		{
			DisplayData(context.Authors.ToList());
			programmingCat = context.Categories
				.Where(c => c.CategoryId == 2)
				.FirstOrDefault();
		}
		
		Book book = new Book()
		{
			Title = "iOS Fundamentals",

			Author = new Author()
			{
				AuthorId = 1,
				Name = "Mark"
			},
			Categories = new List<Category>()
			{
				programmingCat, 
				new Category() { CategoryName = "iOS"},
        		new Category() { CategoryName = "Swift"}
			}
		};
		
		InsertOrUpdate(book);
		
		using(var context = new BookStore())
		{
			Console.WriteLine("\n\n\nAfter Entity Graph\n\n\n");
			DisplayData(context.Authors.ToList());
		}
	}
	
	public static void InsertOrUpdate(Book book)
	{
    	using(var context = new BookStore())
		{
    		context.Entry(book).State = book.BookId == 0 ? 
				EntityState.Added : EntityState.Modified;

    		context.Entry(book.Author).State = book.Author.AuthorId == 0 ? 
				EntityState.Added : EntityState.Modified;

    		foreach (var cat in book.Categories)
			{
        		context.Entry(cat).State = cat.CategoryId == 0 ? 
					EntityState.Added : EntityState.Modified;
			}
			
			context.SaveChanges();
		}
	}
	
	public static void DisplayData(List<Author> list)
	{
		foreach(var author in list)
		{
			Console.WriteLine("Author Name: " + author.Name);
			Console.WriteLine("\tBook List:");
			foreach(var book in author.Books)
			{
				Console.WriteLine("\t\t" + book.Title);
			}
		}
	}
	
	public static void InsertData()
	{
		using (var context = new BookStore())
		{
			Category c1 = new Category() { CategoryName = "C#" };
			Category c2 = new Category() { CategoryName = "Programming" };
			Category c3 = new Category() { CategoryName = "Java" };
			Category c4 = new Category() { CategoryName = "SQL" };
			Category c5 = new Category() { CategoryName = "VB.NET" };

			Author author1 = new Author()
		    {
		        Name = "Mark",
		        Books = new List<Book>
				{
					new Book() { Title = "Fundamentals of Computer Programming with C#", Categories = new List<Category>(){c1, c2}},
					new Book() { Title = "Java: A Beginner's Guide", Categories = new List<Category>(){c3, c2}},
				}
		    };
			Author author2 = new Author()
		    {
		        Name = "Andy",
		        Books = new List<Book>
				{
					new Book() { Title = "SQL: The Ultimate Beginners Guide", Categories = new List<Category>(){c4}}
				}
		    };
			
			Author author3 = new Author()
		    {
		        Name = "Johny",
		        Books = new List<Book>
				{
					new Book() { Title = "Learn VB.NET", Categories = new List<Category>(){c5, c2}},
					new Book() { Title = "C# Fundamentals for Absolute Beginners", Categories = new List<Category>(){c1, c2}},
				}
		    };
			
		    context.Authors.Add(author1);
			context.Authors.Add(author2);
			context.Authors.Add(author3);

		    context.SaveChanges();
		}
	}
	
	public class BookStore : DbContext
    {
        public BookStore() : base(FiddleHelper.GetConnectionStringSqlServer())
        {
        }
	

        public DbSet<Author> Authors { get; set; }
        public DbSet<Book> Books { get; set; }
		public DbSet<Category> Categories { get; set; }
    }

     public class Book
	{
    	public int BookId { get; set; }
	    public string Title { get; set; }
	    public int AuthorId { get; set; }
	    [ForeignKey("AuthorId")]
    	public Author Author { get; set; }
		public virtual ICollection<Category> Categories { get; set; }
	}

    public class Author
	{
    	public int AuthorId { get; set; }
    	public string Name { get; set; }
		public virtual ICollection<Book> Books { get; set; }
	}
	
	public class Category
	{
	    public int CategoryId { get; set; }
	    public string CategoryName { get; set; }
	    public virtual ICollection<Book> Books { get; set; }
	}
}