public void TestMethod3()
{
var scopeFactory = new ContextExtension("demo");
using (var scope = scopeFactory.GetReadOnlyContextScope())
{
var x = TestMethod3_sub(scope);
Console.WriteLine(x.FirstOrDefault());
}
}
static void Main(string[] args)
{
using (var scope = ContextExtension.GetReadOnlyContextScope("demo"))
{
var db = scope.DbContexts.Get <CommonDbContext>();
Console.WriteLine(string.Join(".", db.Users.ToList().Select(c => c.Name)));
var u = from ux in db.Users where ux.Name.Length > 2 select ux.Email;
Console.WriteLine(string.Join(".", u));
}
using (var scope = ContextExtension.GetReadOnlyContextScope("bak"))
{
var db1 = scope.DbContexts.Get <CommonDbContext>();
Console.WriteLine(string.Join(".", db1.Users.ToList().Select(c => c.Name)));
}
//-- 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 DbContextScope within an async flow
Console.WriteLine(
"Trying to retrieve two users John and Jeanne sequentially in an asynchronous manner...");
// We're going to block on the async task here as we don't have a choice. No risk of deadlocking in any case as console apps
// don't have a synchronization context.
var usersFoundAsync = userQueryService.GetTwoUsersAsync(johnSpec.Id, jeanneSpec.Id).Result;
Console.WriteLine("OK. Found {0} persisted users.", usersFoundAsync.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 <CommonDbContext>();
// 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();
}