依赖注入注入参数

我正在使用 DI 的 vNext 实现。 如何向构造函数传递参数？ 比如，我有课:

public class RedisCacheProvider : ICacheProvider
{
private readonly string _connectionString;


public RedisCacheProvider(string connectionString)
{
_connectionString = connectionString;
}
//interface methods implementation...
}

服务登记册:

services.AddSingleton<ICacheProvider, RedisCacheProvider>();

如何将参数传递给 RedisCacheProvider 类的构造函数？ 例如 Autofac:

builder.RegisterType<RedisCacheProvider>()
.As<ICacheProvider>()
.WithParameter("connectionString", "myPrettyLocalhost:6379");
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小开
最佳答案

You can either provide a delegate to manually instantiate your cache provider or directly provide an instance:

services.AddSingleton<ICacheProvider>(provider => new RedisCacheProvider("myPrettyLocalhost:6379"));


services.AddSingleton<ICacheProvider>(new RedisCacheProvider("myPrettyLocalhost:6379"));

Please note that the container will not explicitly dispose of manually instantiated types, even if they implement IDisposable. See the ASP.NET Core doc about Disposal of Services for more info.

小开

If the constructur also has dependencies that should be resolved by DI you can use that:

public class RedisCacheProvider : ICacheProvider
{
private readonly string _connectionString;
private readonly IMyInterface _myImplementation;


public RedisCacheProvider(string connectionString, IMyInterface myImplementation)
{
_connectionString = connectionString;
_myImplementation = myImplementation;
}
//interface methods implementation...
}

Startup.cs:

services.AddSingleton<IMyInterface, MyInterface>();
services.AddSingleton<ICacheProvider>(provider =>
RedisCacheProvider("myPrettyLocalhost:6379", provider.GetService<IMyInterface>()));
小开

A bit late to the party, but you could DI inject a factory that creates and exposes an instance of your provider class.

小开

You can use :

 services.AddSingleton<ICacheProvider>(x =>
ActivatorUtilities.CreateInstance<RedisCacheProvider>(x, "myPrettyLocalhost:6379"));

Dependency Injection : ActivatorUtilities will inject any dependencies to your class.

Here is the link to the MS docs: Microsoft.Extensions.DependencyInjection.ActivatorUtilities.CreateInstance

Also: See @poke's answer here for more information. Basically it pulls from the provided services and any other params you pass, like a composit constructor.

小开

You can use something like the example code below.

Manager class:

public class Manager : IManager
{
ILogger _logger;
IFactory _factory;
public Manager(IFactory factory, ILogger<Manager> logger)
{
_logger = logger;
_factory = factory;
}
}

Startup.cs class:

public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton<IFactory, Factory>(sp =>
{
var logger = sp.GetRequiredService<ILogger<Factory>>();
var dbContext = sp.GetRequiredService<MyDBContext>();
return new Factory(dbContext, logger);
});
services.AddTransient<IManager, Manager>(sp =>
{
var factory = sp.GetRequiredService<IFactory>();
var logger = sp.GetRequiredService<ILogger<Manager>>();
return new Manager(factory, logger);
});
}

You can read the full example here: DI in Startup.cs in .Net Core


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