With EF Core, DbContext is registered as Scoped by EF service extension. This is desirable because DbContext is not thread-safe and therefore it should be created per request.
ServiceStack IOC treats any Scoped registration in Startup as singleton, which contradicts with the point above.
One possible solution is to not use EF Core's service extension, but that seems to bring a lot of boilerplate code and reduce maintainability. Is there any better way?
--
UPDATE
I'd like to provide sample code for clarity
I added a private Guid to the DbContext class so that I can tell whether we have the new instance.
public class BloggingContext : DbContext
{
private readonly Guid _instance;
public BloggingContext(DbContextOptions<BloggingContext> options)
: base(options)
{
_instance = Guid.NewGuid();
}
public DbSet<Blog> Blogs { get; set; }
}
With .NET Core MVC, the controller code looks like
public class BlogsController : Controller
{
private readonly BloggingContext _context;
public BlogsController(BloggingContext context)
{
_context = context;
}
// skip for readability
}
For each request hitting the controller, the _instance inside BloggingContext returns an unique value. However, when using within a ServiceStack service, _instance always returns the same value.
public class BlogService : ServiceStack.Service
{
private readonly BloggingContext _context;
public BlogService(BloggingContext context)
{
_context = context;
}
// skip for readability
}
This behaviour is consistent with ServiceStack documentation about .NET Core Container Adapter that scoped dependencies registered in .NET Core Startup is singleton within ServiceStack. However, it is not desirable because we want DbContext to be created per request.
My solution is that I move the DbContext registration into AppHost code as below
public override void Configure(Container container)
{
container.AddScoped(c =>
{
var optionsBuilder = new DbContextOptionsBuilder<BloggingContext>();
optionsBuilder.UseSqlServer(connection);
return new BloggingContext(optionsBuilder.Options);
});
}
This code works as I expect. Every instance of BloggingContext injected into my BlogService is now unique. However, I find myself unable to use any service collection extension which is very handy in .Net Core Startup anymore. For example, I want to use Entity Framework Unit Of Work and I couldn't call
services
.AddUnitOfWork<BloggingContext>();
Instead, I have to wire up all dependencies of that library myself like
public override void Configure(Container container)
{
container.AddScoped(c =>
{
var optionsBuilder = new DbContextOptionsBuilder<BloggingContext>();
optionsBuilder.UseSqlServer(connection);
return new BloggingContext(optionsBuilder.Options);
});
container.AddScoped<IRepositoryFactory, UnitOfWork<BloggingContext>>();
container.AddScoped<IUnitOfWork, UnitOfWork<BloggingContext>>();
container.AddScoped<IUnitOfWork<BloggingContext>, UnitOfWork<BloggingContext>>();
}
You should be able to register it in .NET Core's IOC like any .NET Core App:
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<BloggingContext>(options =>
options.UseSqlite("Data Source=blog.db"));
}
Then reference like a normal dependency in your ServiceStack Services:
public class MyServices : Service
{
public BloggingContext BloggingContext { get; set; }
}
Which uses ServiceStack's .NET Core Container Adapter to resolve any dependencies not in ServiceStack's IOC, in .NET Core's IOC.
I'm creating an webapi application in dotnet core with entity framework. When I gone through documentation. I can use DI to inject the dbcontext object in dotnet core. But when I'm doing this the whole application using one dbcontext object. How do I make the dbcontext as transient? If any example is there it will really help me.
Please find my existing code below.
This is the code I wrote in ConfigureService
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<DataAccess.XXXXContext>(options => options.UseMySQL(Configuration["ConnectionStrings:DefaultConnection"]),ServiceLifetime.Transient);
}
This is the code i wrote in DBcontext class
public partial class XXXXContext : DbContext
{
private readonly Logger logger = LogManager.GetCurrentClassLogger();
public XXXXContext(DbContextOptions<XXXXContext> options) :base(options)
{
logger.Debug("XXXXContext created");
}
}
If you see i have written already Transient in the AddDbContext method.So everytime if it create object. My constructor should call. But i'm getting call only once.
I`ve already done this using a separated statement.
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<DataAccess.XXXXContext>(options => options.UseMySQL(Configuration["ConnectionStrings:DefaultConnection"]));
services.AddTransient<DataAccess.XXXXContext>();
}
I am using Entity Framework 7 on the nightly build channel (right now I'm using version EntityFramework.7.0.0-beta2-11524) and I'm trying to log the queries that EF generates just out of curiosity.
I'm writing a simple console program, I tried using the same logging technic that EF6 uses, but DbContext.Database.Logis not available on Entity Framework 7. Is there a way to log or just take a peek at the SQL generated by EF7?
For those using EF7 none of the above worked for me. But this is how i got it working. (from #avi cherry's comment)
In your Startup.cs you proably have a Configure method with a bunch of configurations in it. It should look like below (in addition to your stuff).
public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
{
//this is the magic line
loggerFactory.AddDebug(LogLevel.Debug); // formerly LogLevel.Verbose
//your other stuff
}
You can log to the console using this code, I am sure it will be wrapped in a simpler api later:
using System;
using Microsoft.Data.Entity.Infrastructure;
using Microsoft.Data.Entity.Utilities;
using Microsoft.Framework.Logging;
public static class SqlCeDbContextExtensions
{
public static void LogToConsole(this DbContext context)
{
var loggerFactory = ((IAccessor<IServiceProvider>)context).GetService<ILoggerFactory>();
loggerFactory.AddProvider(new DbLoggerProvider());
}
}
And the DbLoggerProvider is implemented here: https://github.com/ErikEJ/EntityFramework7.SqlServerCompact/tree/master/src/Provider40/Extensions/Logging
If you are using MS SQL Server, one way I have used in the past is to make use of the SQL Server Profiler and capture all interaction with the SQL Server, this captures the exact SQL submitted and can be cut n pasted into the SQL Server Management Studio for further review/analysis.
I know this does not directly answer your question on Entity Framework, but I have found this generic approach very useful for any language/tools.
One tip is in the Trace Properties when setting up a new trace, I have found it useful to adjust the default selection of events in the Events Selection tab. Mostly I turn off the Audit Login/Logout unless specifically tracking such an issue.
I struggled with all the above answers as the EF bits kept changing, so the code wouldn't compile. As of today (19Feb2016) with EF7.0.0-rc1-final (Prerelease) and SQLite, here's what works for me:
From the EF7 documentation:
using System;
using System.IO;
using Microsoft.Extensions.Logging;
namespace EFLogging
{
public class EFLoggerProvider : ILoggerProvider
{
public ILogger CreateLogger(string categoryName)
{
return new EFLogger();
}
public void Dispose()
{
// N/A
}
private class EFLogger : ILogger
{
public IDisposable BeginScopeImpl(object state)
{
return null;
}
public bool IsEnabled(LogLevel logLevel)
{
return true;
}
public void Log(LogLevel logLevel, int eventId, object state, Exception exception, Func<object, Exception, string> formatter)
{
File.AppendAllText(#".\EF.LOG", formatter(state, exception));
Console.WriteLine(formatter(state, exception));
}
}
}
}
Using some ideas above and the EF7 Docs:
using System;
using Microsoft.Data.Entity;
using Microsoft.Data.Entity.Infrastructure;
using Microsoft.Extensions.DependencyInjection; // Add this to EF7 docs code
using Microsoft.Extensions.Logging;
namespace DataAccessLayer
{
public static class DbContextExtensions
{
public static void LogToConsole(this DbContext context)
{
var serviceProvider = context.GetInfrastructure<IServiceProvider>();
var loggerFactory = serviceProvider.GetService<ILoggerFactory>();
loggerFactory.AddProvider(new EFLoggerProvider(logLevel));
}
}
}
EDIT: #jnm2 pointed out if you add "using Microsoft.Extensions.DependencyInjection", the EF7 docs ARE correct. Thanks!
And finally, in my App.OnStartup method:
using (var db = new MyDbContext())
{
db.LogToConsole();
}
This code will create a log file and also output logging info to the Visual Studio output window. I hope this helps -- I'm sure in a few weeks, the bits will change again.
With the latest version of EF7-beta8, Anthony's answer need a little tweaking. Here's what I did to get it to work.
internal static class DbContextExtensions
{
public static void LogToConsole(this DbContext context)
{
var loggerFactory = context.GetService<ILoggerFactory>();
loggerFactory.AddConsole(LogLevel.Verbose);
}
}
I think I figured this out. With the current EF7 bits, ILoggerFactory is registered with the dependency injection container which EF is using. You can get a reference to the container, which is an IServiceProvider, via the ScopedServiceProvider property of DbContext when it is cast to IDbContextServices. From there, you can get the ILoggerFactory and configure it using the AddToConsole extension method from the Microsoft.Framework.Logging.Console NuGet package.
public static void LogToConsole(this DbContext context)
{
// IServiceProvider represents registered DI container
IServiceProvider contextServices = ((IDbContextServices)context).ScopedServiceProvider;
// Get the registered ILoggerFactory from the DI container
var loggerFactory = contextServices.GetRequiredService<ILoggerFactory>();
// Add a logging provider with a console trace listener
loggerFactory.AddConsole(LogLevel.Verbose);
}
Here is a gist I created for this snippet: https://gist.github.com/tonysneed/4cac4f4dae2b22e45ec4
This worked for me with EF7 rc2-16485:
"EntityFramework.MicrosoftSqlServer": "7.0.0-rc2-16485",
"Microsoft.Extensions.Logging.Console": "1.0.0-rc2-15888",
public static class DbContextExtensions
{
public static void LogToConsole(this DbContext context)
{
var contextServices = ((IInfrastructure<IServiceProvider>) context).Instance;
var loggerFactory = contextServices.GetRequiredService<ILoggerFactory>();
loggerFactory.AddConsole(LogLevel.Verbose);
}
}
As an alternative to the above answers, I found this answer by far the easiest solution for me to reason about:
private readonly ILoggerFactory loggerFactory;
// Using dependency injection
public FooContext(ILoggerFactory loggerFactor) {
this.loggerFactory = loggerFactory;
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) {
optionsBuilder.UseLoggerFactory(loggerFactory); // Register logger in context
}
With ASP.NET Core 2.0 you get SQL logging automatically. No need to do anything extra.
For those who just want SQL queries to be logged (using Entity Framework Core with .NET Core 2.0 or above), use the following code in your DbContext class:
public static readonly LoggerFactory MyLoggerFactory
= new LoggerFactory(new[]
{
new ConsoleLoggerProvider((category, level)
=> category == DbLoggerCategory.Database.Command.Name
&& level == LogLevel.Information, true)
});
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
=> optionsBuilder
.UseLoggerFactory(MyLoggerFactory) // Warning: Do not create a new ILoggerFactory instance each time
.UseSqlServer(
#"Server=(localdb)\mssqllocaldb;Database=EFLogging;Trusted_Connection=True;ConnectRetryCount=0");
Reference: https://learn.microsoft.com/en-us/ef/core/miscellaneous/logging
I am using Ninject in my ASP MVC 3 project, I have modified the global.asax file (as normally done) and then created a class NinjectControllerFactory like this:
public class NinjectControllerFactory : DefaultControllerFactory
{
private IKernel ninjectKernel;
public NinjectControllerFactory()
{
ninjectKernel = new StandardKernel();
AddBindings();
}
protected override IController GetControllerInstance(RequestContext requestContext,
Type controllerType)
{
return controllerType == null
? null
: (IController)ninjectKernel.Get(controllerType);
}
private void AddBindings()
{
// put additional bindings here
ninjectKernel.Bind<IServiceName>().To<ConcreteClass>();
}
}
All this works fine.
Now I want to add my Entity framework context object to the binding, so that I do not have to create a new instance of it for each service.
Can anyone tell how to do it?
Should I create a new interface which just defines a Entity framework context?
Thanks
You could use self-binding
kernel.Bind<MyDbContext>().ToSelf();
P.S you should also check-out Ninject.MVC3 package on nuget
I have been using autofac with MVC 3 for a while and love it. I recently upgraded a project to MVC 4 and everything seems to be working except for Web Api ApiControllers. I am getting the following exception.
An error occurred when trying to create a controller of type 'MyNamespace.Foo.CustomApiController'. Make sure that the controller has a parameterless public constructor.
This seems to me to be an issue with DI via autofac. Am I missing something or is there something in the works. I know, MVC4 just came out and is a beta so I don't expect much but figured I could be missing something.
I have released Autofac integration packages on NuGet for the Beta versions of MVC 4 and Web API. The integrations will create an Autofac lifetime scope per controller request (MVC controller or API controller depending on the integration). This means that the controller and its dependencies will be automatically disposed at the end of each call. Both packages can be installed side-by-side in the same project.
MVC 4
https://nuget.org/packages/Autofac.Mvc4
http://alexmg.com/post/2012/03/09/Autofac-ASPNET-MVC-4-(Beta)-Integration.aspx
Web API
https://nuget.org/packages/Autofac.WebApi/
http://alexmg.com/post/2012/03/09/Autofac-ASPNET-Web-API-(Beta)-Integration.aspx
Links are now fixed.
I just configured this on one of my apps. There are different ways of doing it but I like this approach:
Autofac and ASP.NET Web API System.Web.Http.Services.IDependencyResolver Integration
First I created a class which implements System.Web.Http.Services.IDependencyResolver interface.
internal class AutofacWebAPIDependencyResolver : System.Web.Http.Services.IDependencyResolver {
private readonly IContainer _container;
public AutofacWebAPIDependencyResolver(IContainer container) {
_container = container;
}
public object GetService(Type serviceType) {
return _container.IsRegistered(serviceType) ? _container.Resolve(serviceType) : null;
}
public IEnumerable<object> GetServices(Type serviceType) {
Type enumerableServiceType = typeof(IEnumerable<>).MakeGenericType(serviceType);
object instance = _container.Resolve(enumerableServiceType);
return ((IEnumerable)instance).Cast<object>();
}
}
And I have another class which holds my registrations:
internal class AutofacWebAPI {
public static void Initialize() {
var builder = new ContainerBuilder();
GlobalConfiguration.Configuration.ServiceResolver.SetResolver(
new AutofacWebAPIDependencyResolver(RegisterServices(builder))
);
}
private static IContainer RegisterServices(ContainerBuilder builder) {
builder.RegisterAssemblyTypes(typeof(MvcApplication).Assembly).PropertiesAutowired();
builder.RegisterType<WordRepository>().As<IWordRepository>();
builder.RegisterType<MeaningRepository>().As<IMeaningRepository>();
return
builder.Build();
}
}
Then, initialize it at Application_Start:
protected void Application_Start() {
//...
AutofacWebAPI.Initialize();
//...
}
I hope this helps.