How to setup with navigation properties

问题:

I am trying to set up a simple library application in MVC4

I have the following entities

public class Book
{
    public Book()
    {
        BorrowedBooks = new List<BorrowedBooks>();

    }
    public int Id { get; set; }
    public string Title { get; set; }
    public string Author { get; set; }        
    public virtual ICollection<BorrowedBooks> BorrowedBooks { get; set; }
}
 public class Borrower
{
    public Borrower()
    {
        BorrowedBooks = new List<BorrowedBooks>();
    }
    public int Id { get; set; }
    public string Firstname { get; set; }
    public string Lastname { get; set; }


    public virtual ICollection<BorrowedBooks> BorrowedBooks { get; set; }
}
 public class BorrowedBooks
{
    public int Id { get; set; }
    public int BookId { get; set; }
    public int BorrowerId { get; set; }
    public DateTime DateBorrowed { get; set; }

    public virtual Book Book { get; set; }
    public virtual Borrower Borrower { get; set; }

}

I have setup 2 repositories

 public class BookRepository : IBookRepository
    {
        private List<Book> books = new List<Book>
            {
                new Book { Id = 1, Title = "Queen of the road", Author = "Tricia Stringer", BorrowedBooks = new List<BorrowedBooks>{  new BorrowedBooks {BookId = 1, BorrowerId = 1, DateBorrowed = DateTime.Parse("26/03/2014")}} },
                new Book { Id = 2, Title = "Don't look now", Author = "Paul Jennings" },
                new Book { Id = 3, Title = "Too bold to die", Author = "Ian McPhedran" },
                new Book { Id = 4, Title = "The rosie project", Author = "Graeme Simson" },
                new Book { Id = 5, Title = "In great spirits", Author = "Archie Barwick" },
                new Book { Id = 6, Title = "The vale girl", Author = "Nelika Mcdonald" },
                new Book { Id = 7, Title = "Watching you", Author = "Michael Robotham" },
                new Book { Id = 8, Title = "Stillways", Author = "Steve Bisley" },
            };

        private List<BorrowedBooks> borrowedBooks = new List<BorrowedBooks>
            {
                new BorrowedBooks {BookId = 8, Book = new Book { Id = 8, Title = "Stillways", Author = "Steve Bisley" },   BorrowerId = 2,  DateBorrowed = DateTime.Parse("01/04/2014")},
                new BorrowedBooks {BookId = 6, BorrowerId = 4, DateBorrowed = DateTime.Parse("08/04/2014")},
                new BorrowedBooks {BookId = 2, BorrowerId = 4, DateBorrowed = DateTime.Parse("08/04/2014")},
                new BorrowedBooks {BookId = 1, BorrowerId = 1, DateBorrowed = DateTime.Parse("26/03/2014")},

            };

        public IEnumerable<Book> Search()
        {

            return books;

        }

    }



public class BorrowerRepository : IBorrowerRepository
    {
        private List<Borrower> borrowers = new List<Borrower>
            {
                new Borrower { Id = 1, Firstname = "John", Lastname = "Smith" },
                new Borrower { Id = 2, Firstname = "Mary", Lastname = "Jane" },
                new Borrower { Id = 3, Firstname = "Peter", Lastname = "Parker" },
                new Borrower { Id = 4, Firstname = "Eddie", Lastname = "Brock" },
            };


        public void Add(Borrower borrower)
        {
            this.borrowers.Add(borrower);
        }
    }

How do I link the properties together? ie in my BorrowerRepository search method, it return all the data, but the Book value is just an ID, how do I link it with the values from the book repository?

have I set up my navigation property wrong? or is it the way I have set up my Repository data?

回答1:

One way to achieve that is to add a static class to hold collections of your data in memory. Then in each of your repositories you delegate any data related operation to the appropriate collections in the data store and you can use Linq to do your queries.

 public static class DataStore
{
    private static List<Book> books = new List<Book>
        {
            new Book { Id = 1, Title = "Queen of the road", Author = "Tricia Stringer", BorrowedBooks = new List<BorrowedBooks>{  new BorrowedBooks {BookId = 1, BorrowerId = 1, DateBorrowed = DateTime.Parse("26/03/2014")}} },
            new Book { Id = 2, Title = "Don't look now", Author = "Paul Jennings" },
            new Book { Id = 3, Title = "Too bold to die", Author = "Ian McPhedran" },
            new Book { Id = 4, Title = "The rosie project", Author = "Graeme Simson" },
            new Book { Id = 5, Title = "In great spirits", Author = "Archie Barwick" },
            new Book { Id = 6, Title = "The vale girl", Author = "Nelika Mcdonald" },
            new Book { Id = 7, Title = "Watching you", Author = "Michael Robotham" },
            new Book { Id = 8, Title = "Stillways", Author = "Steve Bisley" },
        };

    private static List<BorrowedBooks> borrowedBooks = new List<BorrowedBooks>
        {
            new BorrowedBooks {BookId = 8, Book = new Book { Id = 8, Title = "Stillways", Author = "Steve Bisley" },   BorrowerId = 2,  DateBorrowed = DateTime.Parse("01/04/2014")},
            new BorrowedBooks {BookId = 6, BorrowerId = 4, DateBorrowed = DateTime.Parse("08/04/2014")},
            new BorrowedBooks {BookId = 2, BorrowerId = 4, DateBorrowed = DateTime.Parse("08/04/2014")},
            new BorrowedBooks {BookId = 1, BorrowerId = 1, DateBorrowed = DateTime.Parse("26/03/2014")},

        };

    private static List<Borrower> borrowers = new List<Borrower>
        {
            new Borrower { Id = 1, Firstname = "John", Lastname = "Smith" },
            new Borrower { Id = 2, Firstname = "Mary", Lastname = "Jane" },
            new Borrower { Id = 3, Firstname = "Peter", Lastname = "Parker" },
            new Borrower { Id = 4, Firstname = "Eddie", Lastname = "Brock" },
        };

    public static List<Book> Books { get { return books; } }
    public static List<BorrowedBooks> BorrowedBooks { get { return borrowedBooks; } }
    public static List<Borrower> Borrowers { get { return borrowers; } }
}

public class BookRepository : IBookRepository
{
    public IEnumerable<Book> Search()
    {

        return DataStore.Books.Where (b => b.Author == "Paul Jennings");
    }
}

public class BorrowerRepository : IBorrowerRepository
{
    public void Add(Borrower borrower)
    {
        DataStore.Borrowers.Add(borrower);
    }
}