public void CreateUser(UserCreationSpec userToCreate)
{
if (userToCreate == null)
throw new ArgumentNullException("userToCreate");
userToCreate.Validate();
/*
* Typical usage of DbContextScope for a read-write business transaction.
* It's as simple as it looks.
*/
using (var dbContextScope = _dbContextScopeFactory.Create())
{
//-- Build domain model
var user = new User()
{
Id = userToCreate.Id,
Name = userToCreate.Name,
Email = userToCreate.Email,
WelcomeEmailSent = false,
CreatedOn = DateTime.UtcNow
};
//-- Persist
_userRepository.Add(user);
dbContextScope.SaveChanges();
}
}
static void Main(string[] args)
{
//-- Poor-man DI - build our dependencies by hand for this demo
var dbContextScopeFactory = new DbContextScopeFactory();
var ambientDbContextLocator = new AmbientDbContextLocator();
var userRepository = new UserRepository(ambientDbContextLocator);
var userCreationService = new UserCreationService(dbContextScopeFactory, userRepository);
var userQueryService = new UserQueryService(dbContextScopeFactory, userRepository);
var userEmailService = new UserEmailService(dbContextScopeFactory);
var userCreditScoreService = new UserCreditScoreService(dbContextScopeFactory);
try
{
Console.WriteLine("This demo application will create a database named DbContextScopeDemo in the default SQL Server instance on localhost. Edit the connection string in UserManagementDbContext if you'd like to create it somewhere else.");
Console.WriteLine("Press enter to start...");
Console.ReadLine();
//-- Demo of typical usage for read and writes
Console.WriteLine("Creating a user called Mary...");
var marysSpec = new UserCreationSpec("Mary", "*****@*****.**");
userCreationService.CreateUser(marysSpec);
Console.WriteLine("Done.\n");
Console.WriteLine("Trying to retrieve our newly created user from the data store...");
var mary = userQueryService.GetUser(marysSpec.Id);
Console.WriteLine("OK. Persisted user: {0}", mary);
Console.WriteLine("Press enter to continue...");
Console.ReadLine();
//-- Demo of nested DbContextScopes
Console.WriteLine("Creating 2 new users called John and Jeanne in an atomic transaction...");
var johnSpec = new UserCreationSpec("John", "*****@*****.**");
var jeanneSpec = new UserCreationSpec("Jeanne", "*****@*****.**");
userCreationService.CreateListOfUsers(johnSpec, jeanneSpec);
Console.WriteLine("Done.\n");
Console.WriteLine("Trying to retrieve our newly created users from the data store...");
var createdUsers = userQueryService.GetUsers(johnSpec.Id, jeanneSpec.Id);
Console.WriteLine("OK. Found {0} persisted users.", createdUsers.Count());
Console.WriteLine("Press enter to continue...");
Console.ReadLine();
//-- Demo of nested DbContextScopes in the face of an exception.
// If any of the provided users failed to get persisted, none should get persisted.
Console.WriteLine("Creating 2 new users called Julie and Marc in an atomic transaction. Will make the persistence of the second user fail intentionally in order to test the atomicity of the transaction...");
var julieSpec = new UserCreationSpec("Julie", "*****@*****.**");
var marcSpec = new UserCreationSpec("Marc", "*****@*****.**");
try
{
userCreationService.CreateListOfUsersWithIntentionalFailure(julieSpec, marcSpec);
Console.WriteLine("Done.\n");
}
catch (Exception e)
{
Console.WriteLine(e.Message);
Console.WriteLine();
}
Console.WriteLine("Trying to retrieve our newly created users from the data store...");
var maybeCreatedUsers = userQueryService.GetUsers(julieSpec.Id, marcSpec.Id);
Console.WriteLine("Found {0} persisted users. If this number is 0, we're all good. If this number is not 0, we have a big problem.", maybeCreatedUsers.Count());
Console.WriteLine("Press enter to continue...");
Console.ReadLine();
//-- Demo of explicit database transaction.
Console.WriteLine("Trying to retrieve user John within a READ UNCOMMITTED database transaction...");
// You'll want to use SQL Profiler or Entity Framework Profiler to verify that the correct transaction isolation
// level is being used.
var userMaybeUncommitted = userQueryService.GetUserUncommitted(johnSpec.Id);
Console.WriteLine("OK. User found: {0}", userMaybeUncommitted);
Console.WriteLine("Press enter to continue...");
Console.ReadLine();
//-- Demo of disabling the DbContextScope nesting behaviour in order to force the persistence of changes made to entities
// This is a pretty advanced feature that you can safely ignore until you actually need it.
Console.WriteLine("Will simulate sending a Welcome email to John...");
using (var parentScope = dbContextScopeFactory.Create())
{
var parentDbContext = parentScope.DbContexts.Get<UserManagementDbContext>();
// Load John in the parent DbContext
var john = parentDbContext.Users.Find(johnSpec.Id);
Console.WriteLine("Before calling SendWelcomeEmail(), john.WelcomeEmailSent = " + john.WelcomeEmailSent);
// Now call our SendWelcomeEmail() business logic service method, which will
// update John in a non-nested child context
userEmailService.SendWelcomeEmail(johnSpec.Id);
// Verify that we can see the modifications made to John by the SendWelcomeEmail() method
Console.WriteLine("After calling SendWelcomeEmail(), john.WelcomeEmailSent = " + john.WelcomeEmailSent);
// Note that even though we're not calling SaveChanges() in the parent scope here, the changes
// made to John by SendWelcomeEmail() will remain persisted in the database as SendWelcomeEmail()
// forced the creation of a new DbContextScope.
}
Console.WriteLine("Press enter to continue...");
Console.ReadLine();
//-- Demonstration of DbContextScope and parallel programming
Console.WriteLine("Calculating and storing the credit score of all users in the database in parallel...");
userCreditScoreService.UpdateCreditScoreForAllUsers();
Console.WriteLine("Done.");
}
catch (Exception e)
{
Console.WriteLine(e);
}
Console.WriteLine();
Console.WriteLine("The end.");
Console.WriteLine("Press enter to exit...");
Console.ReadLine();
}
