Example #1
0
        /// <summary>
        /// Problem solved by only using 1 db connection or introducing transactions isolation levels
        /// </summary>
        public static void Main()
        {
            using (var db1 = new NorthwindEntities())
            {
                using (var db2 = new NorthwindEntities())
                {
                    Console.WriteLine("First connection altering");
                    Console.WriteLine("Original -> " + db1.Employees.First().City);
                    db1.Employees.First().City = "Changed city";
                    Console.WriteLine("Changed -> " + db1.Employees.First().City);

                    Console.WriteLine("Second connection altering");
                    Console.WriteLine("Original -> " + db2.Employees.First().City);
                    db2.Employees.First().City = "Altered city";
                    Console.WriteLine("Changed -> " + db2.Employees.First().City);

                    db1.SaveChanges();

                    db2.SaveChanges();
                }
            }

            using (var db3 = new NorthwindEntities())
            {
                Console.WriteLine("Final connection altering");
                Console.WriteLine(db3.Employees.First().City);
            }
        }
        public static string AddCustomer(NorthwindEntities northwind, Customer customer)
        {
            northwind.Customers.Add(customer);
            northwind.SaveChanges();

            return "Customer added";
        }
        public static void Main()
        {
            using (var northwind1 = new NorthwindEntities())
            {
                TransactionOptions options = new TransactionOptions();
                options.IsolationLevel = IsolationLevel.Serializable;
                using (var scope = new TransactionScope(TransactionScopeOption.Required, options))
                {
                    using (var northwind2 = new NorthwindEntities())
                    {
                        Customer customer = northwind1.Customers.FirstOrDefault();

                        customer.Country = "NewCountry";

                        Customer customer2 = northwind2.Customers.FirstOrDefault();
                        northwind1.SaveChanges();

                        Console.WriteLine("First connection country ->" + customer.Country);
                        Console.WriteLine("Second connection country ->" + customer2.Country);
                        Console.WriteLine("The second connection works with the old data - dirty read.");
                        scope.Complete();
                    }
                }
            }
        }
        public static string DeleteCustomer(NorthwindEntities northwind, Customer newCustomer)
        {
            var selectedCustomer = northwind.Customers.Where(c => c.CustomerID == newCustomer.CustomerID).FirstOrDefault();
            northwind.Customers.Remove(selectedCustomer);
            northwind.SaveChanges();

            return "Customer deleted";
        }
        /// <summary>
        /// EF works with transactions by default - calling SaveChanges() starts a transaction by default.
        /// However we can use transactions to unify many calling of SaveChanges() as one and if one fails - all fail.
        /// </summary>
        public static void Main()
        {
            using (var db = new NorthwindEntities())
            {
                using (var transaction = db.Database.BeginTransaction())
                {
                    var order = new Order()
                    {
                        CustomerID = "WELLI",
                        EmployeeID = 4
                    };

                    db.Orders.Add(order);

                    var orderDetails1 = new Order_Detail()
                    {
                        OrderID = order.OrderID,
                        ProductID = 5,
                        UnitPrice = 12.34m,
                        Quantity = 100,
                        Discount = 0.2f
                    };

                    var orderDetails2 = new Order_Detail()
                    {
                        OrderID = order.OrderID,
                        ProductID = 3,
                        UnitPrice = 12.34m,
                        Quantity = 100,
                        Discount = 0.2f
                    };

                    var orderDetails3 = new Order_Detail()
                    {
                        OrderID = order.OrderID,
                        ProductID = 4,
                        UnitPrice = 12.34m,
                        Quantity = 100,
                        Discount = 0.2f
                    };

                    db.Order_Details.AddRange(new[] { orderDetails1, orderDetails2, orderDetails3 });

                    try
                    {
                        db.SaveChanges();
                    }
                    catch (System.Exception ex)
                    {
                        System.Console.WriteLine(ex);
                        transaction.Rollback();
                    }

                    transaction.Commit();
                }
            }
        }
Example #6
0
 public static int ModifyCustomer(string contactName, string companyName)
 {
     using (NorthwindEntities db = new NorthwindEntities())
     {
         string id = GetCustomerId(companyName);
         var customer = db.Customers.Where(x => x.CustomerID == id).FirstOrDefault();
         if (customer == null) throw new ArgumentException("The record you are trying to modify doesn't exist!!!");
         customer.CompanyName = companyName;
         customer.ContactName = contactName;
         return db.SaveChanges();
     }
 }
Example #7
0
 public static int DeleteCustomer(string companyName)
 {
     using (NorthwindEntities db = new NorthwindEntities())
     {
         string id = GetCustomerId(companyName);
         if (IsCustomerExists(db, id))
         {
             Customer customer = db.Customers.Where(x => x.CustomerID == id).FirstOrDefault();
             db.Customers.Remove(customer);
             return db.SaveChanges();
         }
         else
         {
             return 0;
         }
     }
 }
        public static void Main()
        {
            using (var northwind = new NorthwindEntities())
            {
                using (var scope = new TransactionScope())
                {
                    for (int i = 0; i < 10; i++)
                    {
                        northwind.Orders.Add(new Order() { ShipAddress = "455, Metropolitan Avenue" });
                    }

                    northwind.SaveChanges();
                    scope.Complete();
                }

                Console.WriteLine("Number of added orders: {0}", northwind.Orders.Where(o => o.ShipAddress == "455, Metropolitan Avenue").Count());
            }
        }
Example #9
0
        public static int InsertCustomer(string contactName, string companyName)
        {
            using (NorthwindEntities db = new NorthwindEntities())
            {

                Customer customer = new Customer()
                {
                    ContactName = contactName,
                    CompanyName = companyName,
                    CustomerID = GetCustomerId(companyName),
                };

                if (IsCustomerExists(db, GetCustomerId(companyName)))
                {
                    throw new ArgumentException("Customer already exist!!!");
                }

                db.Customers.Add(customer);
                return db.SaveChanges();
            }
        }
        public static string ModifyCustomerById(NorthwindEntities northwind, string customerId, Customer newCustomer)
        {
            var selectedCustomer = northwind.Customers.Where(c => c.CustomerID == customerId).FirstOrDefault();

            selectedCustomer.Address = newCustomer.Address;
            selectedCustomer.City = newCustomer.City;
            selectedCustomer.CompanyName = newCustomer.CompanyName;
            selectedCustomer.ContactName = newCustomer.ContactName;
            selectedCustomer.ContactTitle = newCustomer.ContactTitle;
            selectedCustomer.Country = newCustomer.Country;
            selectedCustomer.CustomerDemographics = newCustomer.CustomerDemographics;
            selectedCustomer.Fax = newCustomer.Fax;
            selectedCustomer.Orders = newCustomer.Orders;
            selectedCustomer.Phone = newCustomer.Phone;
            selectedCustomer.PostalCode = newCustomer.PostalCode;
            selectedCustomer.Region = newCustomer.Region;

            northwind.SaveChanges();

            return "Customer modified";
        }
        //TODO: Try to open two different data contexts and perform concurrent changes on the same records. 
        //      What will happen at SaveChanges()? How to deal with it?

        static void Main()
        {
            string companyName = "Concurency Test";
            string contactName = "Concurent1";
            string contactName2 = "Concurent2";

            using (NorthwindEntities db = new NorthwindEntities())
            {
                using(NorthwindEntities db2 = new NorthwindEntities())
                {
                    string id = GetCustomerId(companyName);
                    var customer = db.Customers.Where(x => x.CustomerID == id).FirstOrDefault();
                    var customer2 = db2.Customers.Where(x => x.CustomerID == id).FirstOrDefault();
                    if (customer == null) throw new ArgumentException("The record you are trying to modify doesn't exist!!!");
                    customer.CompanyName = companyName;
                    customer.ContactName = contactName;
                    customer2.ContactName= contactName2;
                    db.SaveChanges();
                    db2.SaveChanges();
                }
            }
        }
        private static void CreateOrder(Order newOrder, int numberOfRepeatsUntillSuccess)
        {
            bool isTransactionSucceed = false;
            using (NorthwindEntities dbContext = new NorthwindEntities())
            {
                using (TransactionScope transaction = new TransactionScope())
                {
                    for (int i = 0; i < numberOfRepeatsUntillSuccess; i++)
                    {
                        try
                        {
                            dbContext.Orders.Add(newOrder);
                            dbContext.SaveChanges();
                            transaction.Complete();
                            isTransactionSucceed = true;
                            break;
                        }
                        catch (UpdateException ex)
                        {
                            if (i == numberOfRepeatsUntillSuccess - 1)
                            {
                                throw new InvalidOperationException("Cannot complete order creation", ex);
                            }
                        }
                    }

                    if (isTransactionSucceed)
                    {
                        // Reset the context since the operation succeeded.
                        Console.WriteLine("Transaction sompited");
                    }
                    else
                    {
                        Console.WriteLine("The operation could not be completed in "
                            + numberOfRepeatsUntillSuccess + " tries.");
                    }
                }
            }
        }
 public static void AddOrder(NorthwindEntities northwind, Order order)
 {
     northwind.Orders.Add(order);
     northwind.SaveChanges();
 }