DD Class9

Repo Pattern

Definition from P of EE http://martinfowler.com/eaaCatalog/repository.html MSDN The Repository Pattern

The repository pattern is a nice way to abstract data fetching logic and easily separate concerns from different layers of your app. It allows of to quickly refactor and swap repos.

First we can start with the cheese definition

 public class Cheese
    {
        
        public int CheeseID { get; set; }
        
        public string CheeseName { get; set; }
        
        public string CheeseDescription { get; set; }
    }

Then interface for the repo

public interface IRepository<T>
    {
        T GetById(int id);
        List<T> GetItems();
        void Add(T entity);
        void Remove(T entity);
    }

Now we want to expand the interface definition to cheeses

/// <summary>
    /// ICheeseRepo Changes the type of the Generic Repo To Cheese
    /// </summary>
    public interface ICheeseRepo : IRepository<Cheese>
    {
        List<Cheese> GetItems();
        List<Cheese> GetCheeses();  //New Method To Get Cheeses
        //May want to expand the definition to get cheese by name
        //Cheese GetByName(string name)
    }

Finally the repo interface can then be implemented like this

public class TestCheeseRepository : ICheeseRepo
    {

        //could grab these from the Application Object
        private static List<Cheese> fakeCheeses =
            new List<Cheese> { new Cheese { CheeseID=1, CheeseName="test1", CheeseDescription = "test desc 1" },
                new Cheese { CheeseID=2, CheeseName="test2", CheeseDescription = "test desc 2" },
                new Cheese { CheeseID=2, CheeseName="test3", CheeseDescription = "test desc 3" }
            };


        #region ICheeseRepo Members
        public List<Cheese> GetItems()
        {
            return GetCheeses();
        }


        public List<Cheese> GetCheeses()
        {
            return fakeCheeses.ToList();
        }

        #endregion

        #region IRepository<Cheese> Members

        public Cheese GetById(int id)
        {
            //linq statement to find cheese by ID
            var currentCheese = from c in fakeCheeses where c.CheeseID == id select c;
            return currentCheese.FirstOrDefault();
        }

        public void Add(Cheese entity)
        {
            fakeCheeses.Add(entity);
        }

        public void Remove(Cheese entity)
        {
            fakeCheeses.Remove(entity);
        }

        #endregion

        //added statement to find cheese by name
        public Cheese GetByName(string name)
        {
            //linq statement to find cheese by name
            var currentCheese = from c in fakeCheeses where c.CheeseName == name select c;
            return currentCheese.FirstOrDefault();
        }
    }

Link to the implememtation http://iam.colum.edu/datadesign/gbrowser.php?file=/App_code/Repo/CheeseRepo.cs

Now to use the Repo

http://iam.colum.edu/datadesign/classsource/repo/Default.aspx

http://iam.colum.edu/datadesign/gbrowser.php?file=/classsource/repo/Default.aspx.cs

ICheeseRepo db = new TestCheeseRepository();
        gv1.DataSource = db.GetCheeses();
        gv1.DataBind();

You can add LINQ helpers to the class

/// <summary>
    /// Cheese Class for Our Repo
    /// </summary>
    [Table(Name = "Cheese")]
    public class Cheese
    {
        [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
        public int CheeseID { get; set; }
        [Column]
        public string CheeseName { get; set; }
        [Column]
        public string CheeseDescription { get; set; }
    }

and then create a new cheese repo

and update your repo initialization

ICheeseRepo db = new CheeseRepository(ConfigurationManager.ConnectionStrings["cheeseConnectionString"].ToString()); 
        gv1.DataSource = db.GetCheeses();
        gv1.DataBind();

LINQ classes in MVC must use the entire namespace

/// <summary>
    /// Cheese Class for Our Repo
    /// </summary>
    [System.Data.Linq.Mapping.Table(Name = "Cheese")]
    public class Cheese
    {
        [System.Data.Linq.Mapping.Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
        public int CheeseID { get; set; }
        [System.Data.Linq.Mapping.Column]
        public string CheeseName { get; set; }
        [System.Data.Linq.Mapping.Column]
        public string CheeseDescription { get; set; }
    }

Homework

Use the repo pattern to create a repo for you own class. The the class should map to a table in your database. The repo should be able to show items in you db, add items and remove items.

Add the repo to your Web from site and your MVC site. The repose should be able to list items from the DB. Either the MVC site or the WebForms site should be able to add and delete items. I'll give 1 pt extra for updating items and 1 pt for adding/deleting in MVC and Web Forms.