'.net core injecting and resolving services
I am trying my hand at .net core web api. I have created a static method for registering my controllers like this:
public static class RegistrationExtensions
{
public static void RegisterApplicationServices(this IServiceCollection services, IServiceProvider serviceProvider)
{
services.RegisterSingletons();
services.RegisterRequests();
services.RegisterTransient(serviceProvider);
}
public static void RegisterSingletons(this IServiceCollection services)
{
services.AddSingleton<Configuration>();
}
public static void RegisterRequests(this IServiceCollection services)
{
services.AddScoped<ISettingsService, SettingsService>();
}
public static void RegisterTransient(this IServiceCollection services, IServiceProvider serviceProvider)
{
var config = serviceProvider.GetService<Configuration>();
services.AddDbContext<InteractiveChoicesContext>(m => m.UseSqlServer(config.ConnectionString));
}
}
As you can see, I want to resolve my Configuration class which contains my ConnectionString, which I pass into the DbContext. Do resolve the Configuration I was trying to use IServiceProvider which is injected into the RegisterApplicationServices method.
To invoke this method, I changed the Startup class's ConfigureServices to this:
public void ConfigureServices(IServiceCollection services, IServiceProvider serviceProvider)
{
services.AddMvc();
services.RegisterApplicationServices(serviceProvider);
}
But when I run my application, I get an error:
The ConfigureServices method must either be parameterless or take only one parameter of type IServiceCollection.
The error is obvious. My question is: How can I resolve the Configuration class in my RegisterTransient method?
Solution 1:[1]
There is actually an overload of AddDbContext
that takes an Action<IServiceProvider, DbContextOptionsBuilder>
which should be exactly what you are looking for.
Ex:
services.AddDbContext<InteractiveChoicesContext>((provider, options) =>
{
var config = provider.GetService<Configuration>();
options.UseSqlServer(config.ConnectionString);
});
I have tested this with v2, v3, and v5. The documentation for this overload, as specified in EF Core 2.0.0 is included verbatim for posterity and relevance
//
// Summary:
// Registers the given context as a service in the
// Microsoft.Extensions.DependencyInjection.IServiceCollection.
// You use this method when using dependency injection in your application, such
// as with ASP.NET. For more information on setting up dependency injection, see
// http://go.microsoft.com/fwlink/?LinkId=526890.
// This overload has an optionsAction that provides the applications
// System.IServiceProvider.
// This is useful if you want to setup Entity Framework to resolve its internal
// services from the primary application service provider. By default, we recommend
// using the other overload, which allows Entity Framework to create and maintain
// its own System.IServiceProvider for internal Entity Framework services.
//
// Parameters:
// serviceCollection:
// The Microsoft.Extensions.DependencyInjection.IServiceCollection to add services
// to.
//
// optionsAction:
// An optional action to configure the Microsoft.EntityFrameworkCore.DbContextOptions
// for the context. This provides an alternative to performing configuration of
// the context by overriding the Microsoft.EntityFrameworkCore.DbContext
// .OnConfiguring(Microsoft.EntityFrameworkCore.DbContextOptionsBuilder)
//
// method in your derived context.
// If an action is supplied here, the
// Microsoft.EntityFrameworkCore.DbContext
// .OnConfiguring(Microsoft.EntityFrameworkCore.DbContextOptionsBuilder)
// method will still be run if it has been overridden on the
// derived context. Microsoft.EntityFrameworkCore.DbContext
// .OnConfiguring(Microsoft.EntityFrameworkCore.DbContextOptionsBuilder)
// configuration will be applied in addition to configuration performed here.
// In order for the options to be passed into your context, you need
// to expose a constructor on your context that takes
// Microsoft.EntityFrameworkCore.DbContextOptions`1
// and passes it to the base constructor of
// Microsoft.EntityFrameworkCore.DbContext.
//
// contextLifetime:
// The lifetime with which to register the DbContext
// service in the container.
//
// optionsLifetime:
// The lifetime with which to register the DbContextOptions
// service in the container.
//
// Type parameters:
// TContext:
// The type of context to be registered.
//
// Returns:
// The same service collection so that multiple calls can be chained.
public static IServiceCollection AddDbContext<TContext>(
[NotNullAttribute] this IServiceCollection serviceCollection,
[CanBeNullAttribute] Action<IServiceProvider, DbContextOptionsBuilder> optionsAction,
ServiceLifetime contextLifetime = ServiceLifetime.Scoped,
ServiceLifetime optionsLifetime = ServiceLifetime.Scoped
) where TContext : DbContext;
Solution 2:[2]
If you have to use your own configuration class instead of using IConfiguration
, you could do this to resolve your IServiceCollection
configured thus far, which in your case already has the registration for your Configuration
singleton:
public static void RegisterTransient(this IServiceCollection services)
{
// Use services registered so far
var serviceProvider = services.BuildServiceProvider();
var config = serviceProvider.GetRequiredService<Configuration>();
services.AddDbContext<InteractiveChoicesContext>(m => m.UseSqlServer(config.ConnectionString));
}
where the BuildServiceProvider()
is an extension method in assembly Microsoft.Extensions.DependencyInjection
, namespace Microsoft.Extensions.DependencyInjection
.
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
Solution | Source |
---|---|
Solution 1 | |
Solution 2 | Jeff P |