Category: Entity Framework

Introduction

Roadmap

REST

Setup database

Web API project

Setup Data Access Layer

Generic Repository and Unit of Work

• It centralizes the data logic or Web service access logic.
• It provides a substitution point for the unit tests.
• It provides a flexible architecture that can be adapted as the overall design of the application evolves.

#region Using Namespaces...

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;

#endregion

namespace DataModel.GenericRepository
{
/// <summary>
    /// Generic Repository class for Entity Operations
    /// </summary>
    /// <typeparam name="TEntity"></typeparam>
    public class GenericRepository where TEntity : class
    {
#region Private member variables...
internal WebApiDbEntities Context;
internal DbSet DbSet;
#endregion

#region Public Constructor...
/// <summary>
        /// Public Constructor,initializes privately declared local variables.
        /// </summary>
        /// <param name="context"></param>
        public GenericRepository(WebApiDbEntities context)
        {
this.Context = context;
this.DbSet = context.Set();
        }
#endregion

#region Public member methods...

/// <summary>
        /// generic Get method for Entities
        /// </summary>
        /// <returns></returns>
        public virtual IEnumerable Get()
        {
            IQueryable query = DbSet;
return query.ToList();
        }

/// <summary>
        /// Generic get method on the basis of id for Entities.
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public virtual TEntity GetByID(object id)
        {
return DbSet.Find(id);
        }

/// <summary>
        /// generic Insert method for the entities
        /// </summary>
        /// <param name="entity"></param>
        public virtual void Insert(TEntity entity)
        {
            DbSet.Add(entity);
        }

/// <summary>
        /// Generic Delete method for the entities
        /// </summary>
        /// <param name="id"></param>
        public virtual void Delete(object id)
        {
            TEntity entityToDelete = DbSet.Find(id);
            Delete(entityToDelete);
        }

/// <summary>
        /// Generic Delete method for the entities
        /// </summary>
        /// <param name="entityToDelete"></param>
        public virtual void Delete(TEntity entityToDelete)
        {
if (Context.Entry(entityToDelete).State == EntityState.Detached)
            {
                DbSet.Attach(entityToDelete);
            }
            DbSet.Remove(entityToDelete);
        }

/// <summary>
        /// Generic update method for the entities
        /// </summary>
        /// <param name="entityToUpdate"></param>
        public virtual void Update(TEntity entityToUpdate)
        {
            DbSet.Attach(entityToUpdate);
            Context.Entry(entityToUpdate).State = EntityState.Modified;
        }

/// <summary>
        /// generic method to get many record on the basis of a condition.
        /// </summary>
        /// <param name="where"></param>
        /// <returns></returns>
        public virtual IEnumerable GetMany(Func<TEntity, bool> where)
        {
return DbSet.Where(where).ToList();
        }

/// <summary>
        /// generic method to get many record on the basis of a condition but query able.
        /// </summary>
        /// <param name="where"></param>
        /// <returns></returns>
        public virtual IQueryable GetManyQueryable(Func<TEntity, bool> where)
        {
return DbSet.Where(where).AsQueryable();
        }

/// <summary>
        /// generic get method , fetches data for the entities on the basis of condition.
        /// </summary>
        /// <param name="where"></param>
        /// <returns></returns>
        public TEntity Get(Func<TEntity, Boolean> where)
        {
return DbSet.Where(where).FirstOrDefault();
        }

/// <summary>
        /// generic delete method , deletes data for the entities on the basis of condition.
        /// </summary>
        /// <param name="where"></param>
        /// <returns></returns>
        public void Delete(Func<TEntity, Boolean> where)
        {
            IQueryable objects = DbSet.Where(where).AsQueryable();
foreach (TEntity obj in objects)
                DbSet.Remove(obj);
        }

/// <summary>
        /// generic method to fetch all the records from db
        /// </summary>
        /// <returns></returns>
        public virtual IEnumerable GetAll()
        {
return DbSet.ToList();
        }

/// <summary>
        /// Inclue multiple
        /// </summary>
        /// <param name="predicate"></param>
        /// <param name="include"></param>
        /// <returns></returns>
        public IQueryable GetWithInclude(
            System.Linq.Expressions.Expression<Func<TEntity, 
bool>> predicate, params string[] include)
        {
            IQueryable query = this.DbSet;
            query = include.Aggregate(query, (current, inc) => current.Include(inc));
return query.Where(predicate);
        }

/// <summary>
        /// Generic method to check if entity exists
        /// </summary>
        /// <param name="primaryKey"></param>
        /// <returns></returns>
        public bool Exists(object primaryKey)
        {
return DbSet.Find(primaryKey) != null;
        }

/// <summary>
        /// Gets a single record by the specified criteria (usually the unique identifier)
        /// </summary>
        /// <param name="predicate">Criteria to match on</param>
        /// <returns>A single record that matches the specified criteria</returns>
        public TEntity GetSingle(Func<TEntity, bool> predicate)
        {
return DbSet.Single(predicate);
        }

/// <summary>
        /// The first record matching the specified criteria
        /// </summary>
        /// <param name="predicate">Criteria to match on</param>
        /// <returns>A single record containing the first record matching the specified criteria</returns>
        public TEntity GetFirst(Func<TEntity, bool> predicate)
        {
return DbSet.First(predicate);
        }


#endregion
    }
}

Unit of Work

• To manage transactions.
• To order the database inserts, deletes, and updates.
• To prevent duplicate updates. Inside a single usage of a Unit of Work object, different parts of the code may mark the same Invoice object as changed, but the Unit of Work class will only issue a single UPDATE command to the database.

#region Using Namespaces...

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Data.Entity.Validation;
using DataModel.GenericRepository;

#endregion

namespace DataModel.UnitOfWork
{
/// <summary>
    /// Unit of Work class responsible for DB transactions
    /// </summary>
    public class UnitOfWork : IDisposable
    {
#region Private member variables...

private WebApiDbEntities _context = null;
private GenericRepository _userRepository;
private GenericRepository _productRepository;
private GenericRepository _tokenRepository;
#endregion

public UnitOfWork()
        {
            _context = new WebApiDbEntities();
        }

#region Public Repository Creation properties...

/// <summary>
        /// Get/Set Property for product repository.
        /// </summary>
        public GenericRepository ProductRepository
        {
get
            {
if (this._productRepository == null)
this._productRepository = new GenericRepository(_context);
return _productRepository;
            }
        }

/// <summary>
        /// Get/Set Property for user repository.
        /// </summary>
        public GenericRepository UserRepository
        {
get
            {
if (this._userRepository == null)
this._userRepository = new GenericRepository(_context);
return _userRepository;
            }
        }

/// <summary>
        /// Get/Set Property for token repository.
        /// </summary>
        public GenericRepository TokenRepository
        {
get
            {
if (this._tokenRepository == null)
this._tokenRepository = new GenericRepository(_context);
return _tokenRepository;
            }
        }
#endregion

#region Public member methods...
/// <summary>
        /// Save method.
        /// </summary>
        public void Save()
        {
try
            {
                _context.SaveChanges();
            }
catch (DbEntityValidationException e)
            {

var outputLines = new List<string>();
foreach (var eve in e.EntityValidationErrors)
                {
                    outputLines.Add(string.Format(
"{0}: Entity of type \"{1}\" in state \"{2}\" has the following validation errors:", DateTime.Now, 
                        eve.Entry.Entity.GetType().Name, eve.Entry.State));
foreach (var ve in eve.ValidationErrors)
                    {
                        outputLines.Add(string.Format("- Property: \"{0}\", Error: \"{1}\"", ve.PropertyName, ve.ErrorMessage));
                    }
                }
                System.IO.File.AppendAllLines(@"C:\errors.txt", outputLines);

throw e;
            }

        }

#endregion

#region Implementing IDiosposable...

#region private dispose variable declaration...
private bool disposed = false; 
#endregion

/// <summary>
        /// Protected Virtual Dispose method
        /// </summary>
        /// <param name="disposing"></param>
        protected virtual void Dispose(bool disposing)
        {
if (!this.disposed)
            {
if (disposing)
                {
                    Debug.WriteLine("UnitOfWork is being disposed");
                    _context.Dispose();
                }
            }
this.disposed = true;
        }

/// <summary>
        /// Dispose method
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        } 
#endregion
    }
}

Setup Business Entities

Product entity

public class ProductEntity
    {
public int ProductId { get; set; }
public string ProductName { get; set; }
    }

Token entity

public class TokenEntity
    {
public int TokenId { get; set; }
public int UserId { get; set; }
public string AuthToken { get; set; }
public System.DateTime IssuedOn { get; set; }
public System.DateTime ExpiresOn { get; set; }
    }

User entity

public class UserEntity
    {
public int UserId { get; set; }
public string UserName { get; set; }
public string Password { get; set; }
public string Name { get; set; }
    }

Setup Business Services Project

using System.Collections.Generic;
using BusinessEntities;

namespace BusinessServices
{
/// <summary>
    /// Product Service Contract
    /// </summary>
    public interface IProductServices
    {
        ProductEntity GetProductById(int productId);
        IEnumerable GetAllProducts();
int CreateProduct(ProductEntity productEntity);
bool UpdateProduct(int productId,ProductEntity productEntity);
bool DeleteProduct(int productId);
    }
}

private readonly UnitOfWork _unitOfWork;

/// <summary>
        /// Public constructor.
        /// </summary>
        public ProductServices()
        {
            _unitOfWork = new UnitOfWork();
        }

using System.Collections.Generic;
using System.Linq;
using System.Transactions;
using AutoMapper;
using BusinessEntities;
using DataModel;
using DataModel.UnitOfWork;

namespace BusinessServices
{
/// <summary>
    /// Offers services for product specific CRUD operations
    /// </summary>
    public class ProductServices:IProductServices
    {
private readonly UnitOfWork _unitOfWork;

/// <summary>
        /// Public constructor.
        /// </summary>
        public ProductServices()
        {
            _unitOfWork = new UnitOfWork();
        }

/// <summary>
        /// Fetches product details by id
        /// </summary>
        /// <param name="productId"></param>
        /// <returns></returns>
        public BusinessEntities.ProductEntity GetProductById(int productId)
        {
var product = _unitOfWork.ProductRepository.GetByID(productId);
if (product != null)
            {
                Mapper.CreateMap();
var productModel = Mapper.Map(product);
return productModel;
            }
return null;
        }

/// <summary>
        /// Fetches all the products.
        /// </summary>
        /// <returns></returns>
        public IEnumerable GetAllProducts()
        {
var products = _unitOfWork.ProductRepository.GetAll().ToList();
if (products.Any())
            {
                Mapper.CreateMap();
var productsModel = Mapper.Map<List, List>(products);
return productsModel;
            }
return null;
        }

/// <summary>
        /// Creates a product
        /// </summary>
        /// <param name="productEntity"></param>
        /// <returns></returns>
        public int CreateProduct(BusinessEntities.ProductEntity productEntity)
        {
using (var scope = new TransactionScope())
            {
var product = new Product
                {
                    ProductName = productEntity.ProductName
                };
                _unitOfWork.ProductRepository.Insert(product);
                _unitOfWork.Save();
                scope.Complete();
return product.ProductId;
            }
        }

/// <summary>
        /// Updates a product
        /// </summary>
        /// <param name="productId"></param>
        /// <param name="productEntity"></param>
        /// <returns></returns>
        public bool UpdateProduct(int productId, BusinessEntities.ProductEntity productEntity)
        {
var success = false;
if (productEntity != null)
            {
using (var scope = new TransactionScope())
                {
var product = _unitOfWork.ProductRepository.GetByID(productId);
if (product != null)
                    {
                        product.ProductName = productEntity.ProductName;
                        _unitOfWork.ProductRepository.Update(product);
                        _unitOfWork.Save();
                        scope.Complete();
                        success = true;
                    }
                }
            }
return success;
        }

/// <summary>
        /// Deletes a particular product
        /// </summary>
        /// <param name="productId"></param>
        /// <returns></returns>
        public bool DeleteProduct(int productId)
        {
var success = false;
if (productId > 0)
            {
using (var scope = new TransactionScope())
                {
var product = _unitOfWork.ProductRepository.GetByID(productId);
if (product != null)
                    {

                        _unitOfWork.ProductRepository.Delete(product);
                        _unitOfWork.Save();
                        scope.Complete();
                        success = true;
                    }
                }
            }
return success;
        }
    }
}

1. To get product by id ( GetproductById ) : We call repository to get the product by id. Id comes as a parameter from the calling method to that service method. It returns the product entity from the database. Note that it will not return the exact db entity, instead we’ll map it with our business entity usingAutoMapper and return it to calling method.

   /// <summary>
           /// Fetches product details by id
           /// </summary>
           /// <param name="productId"></param>
           /// <returns></returns>
           public BusinessEntities.ProductEntity GetProductById(int productId)
           {
   var product = _unitOfWork.ProductRepository.GetByID(productId);
   if (product != null)
               {
                   Mapper.CreateMap();
   var productModel = Mapper.Map(product);
   return productModel;
               }
   return null;
           }

2. Get all products from database (GetAllProducts) : This method returns all the products residing in database, again we make use of AutoMapper to map the list and return back.

   /// <summary>
           /// Fetches all the products.
           /// </summary>
           /// <returns></returns>
           public IEnumerable GetAllProducts()
           {
   var products = _unitOfWork.ProductRepository.GetAll().ToList();
   if (products.Any())
               {
                   Mapper.CreateMap();
   var productsModel = Mapper.Map<List, List>(products);
   return productsModel;
               }
   return null;
           }

3. Create a new product (CreateProduct) : This method takes productBusinessEntity as an argument and creates a new object of actual database entity and insert it using unit of work.

   /// <summary>
           /// Creates a product
           /// </summary>
           /// <param name="productEntity"></param>
           /// <returns></returns>
           public int CreateProduct(BusinessEntities.ProductEntity productEntity)
           {
   using (var scope = new TransactionScope())
               {
   var product = new Product
                   {
                       ProductName = productEntity.ProductName
                   };
                   _unitOfWork.ProductRepository.Insert(product);
                   _unitOfWork.Save();
                   scope.Complete();
   return product.ProductId;
               }
           }

using System.Collections.Generic;
using System.Linq;
using System.Transactions;
using AutoMapper;
using BusinessEntities;
using DataModel;
using DataModel.UnitOfWork;

namespace BusinessServices
{
/// <summary>
    /// Offers services for product specific CRUD operations
    /// </summary>
    public class ProductServices:IProductServices
    {
private readonly UnitOfWork _unitOfWork;

/// <summary>
        /// Public constructor.
        /// </summary>
        public ProductServices()
        {
            _unitOfWork = new UnitOfWork();
        }

/// <summary>
        /// Fetches product details by id
        /// </summary>
        /// <param name="productId"></param>
        /// <returns></returns>
        public BusinessEntities.ProductEntity GetProductById(int productId)
        {
var product = _unitOfWork.ProductRepository.GetByID(productId);
if (product != null)
            {
                Mapper.CreateMap();
var productModel = Mapper.Map(product);
return productModel;
            }
return null;
        }

/// <summary>
        /// Fetches all the products.
        /// </summary>
        /// <returns></returns>
        public IEnumerable GetAllProducts()
        {
var products = _unitOfWork.ProductRepository.GetAll().ToList();
if (products.Any())
            {
                Mapper.CreateMap();
var productsModel = Mapper.Map<List, List>(products);
return productsModel;
            }
return null;
        }

/// <summary>
        /// Creates a product
        /// </summary>
        /// <param name="productEntity"></param>
        /// <returns></returns>
        public int CreateProduct(BusinessEntities.ProductEntity productEntity)
        {
using (var scope = new TransactionScope())
            {
var product = new Product
                {
                    ProductName = productEntity.ProductName
                };
                _unitOfWork.ProductRepository.Insert(product);
                _unitOfWork.Save();
                scope.Complete();
return product.ProductId;
            }
        }

/// <summary>
        /// Updates a product
        /// </summary>
        /// <param name="productId"></param>
        /// <param name="productEntity"></param>
        /// <returns></returns>
        public bool UpdateProduct(int productId, BusinessEntities.ProductEntity productEntity)
        {
var success = false;
if (productEntity != null)
            {
using (var scope = new TransactionScope())
                {
var product = _unitOfWork.ProductRepository.GetByID(productId);
if (product != null)
                    {
                        product.ProductName = productEntity.ProductName;
                        _unitOfWork.ProductRepository.Update(product);
                        _unitOfWork.Save();
                        scope.Complete();
                        success = true;
                    }
                }
            }
return success;
        }

/// <summary>
        /// Deletes a particular product
        /// </summary>
        /// <param name="productId"></param>
        /// <returns></returns>
        public bool DeleteProduct(int productId)
        {
var success = false;
if (productId > 0)
            {
using (var scope = new TransactionScope())
                {
var product = _unitOfWork.ProductRepository.GetByID(productId);
if (product != null)
                    {

                        _unitOfWork.ProductRepository.Delete(product);
                        _unitOfWork.Save();
                        scope.Complete();
                        success = true;
                    }
                }
            }
return success;
        }
    }
}

Setup WebAPI project

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;

namespace WebApi.Controllers
{
public class ProductController : ApiController
    {
// GET api/product
        public IEnumerable<string> Get()
        {
return new string[] { "value1", "value2" };
        }

// GET api/product/5
        public string Get(int id)
        {
return "value";
        }

// POST api/product
        public void Post([FromBody]string value)
        {
        }

// PUT api/product/5
        public void Put(int id, [FromBody]string value)
        {
        }

// DELETE api/product/5
        public void Delete(int id)
        {
        }
    }
}

using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using BusinessEntities;
using BusinessServices;

namespace WebApi.Controllers
{
public class ProductController : ApiController
    {

private readonly IProductServices _productServices;

#region Public Constructor

/// <summary>
        /// Public constructor to initialize product service instance
        /// </summary>
        public ProductController()
        {
            _productServices =new ProductServices();
        }

#endregion

// GET api/product
        public HttpResponseMessage Get()
        {
var products = _productServices.GetAllProducts();
if (products != null)
            {
var productEntities = products as List ?? products.ToList();
if (productEntities.Any())
return Request.CreateResponse(HttpStatusCode.OK, productEntities);
            }
return Request.CreateErrorResponse(HttpStatusCode.NotFound, "Products not found");
        }

// GET api/product/5
        public HttpResponseMessage Get(int id)
        {
var product = _productServices.GetProductById(id);
if (product != null)
return Request.CreateResponse(HttpStatusCode.OK, product);
return Request.CreateErrorResponse(HttpStatusCode.NotFound, "No product found for this id");
        }

// POST api/product
        public int Post([FromBody] ProductEntity productEntity)
        {
return _productServices.CreateProduct(productEntity);
        }

// PUT api/product/5
        public bool Put(int id, [FromBody]ProductEntity productEntity)
        {
if (id  > 0)
            {
return _productServices.UpdateProduct(id, productEntity);
            }
return false;
        }

// DELETE api/product/5
        public bool Delete(int id)
        {
if (id > 0)
return _productServices.DeleteProduct(id);
return false;
        }
    }
}

Running the Application

Design Flaws

1. Architecture is tightly coupled. IOC (Inversion of Control) needs to be there.
2. We cannot define our own routes.
3. No exception handling and logging.
4. No unit tetsts.

Conclusion