Question

我正在使用DI的vNext实现。如何将参数传递给构造函数？例如，我有课：

public class RedisCacheProvider : ICacheProvider
{
    private readonly string _connectionString;

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

服务注册：

services.AddSingleton<ICacheProvider, RedisCacheProvider>();

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

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

Answer 1

您可以提供委托来手动实例化缓存提供程序，也可以直接提供实例：

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

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

请注意，即使容器实现了IDisposable，容器也不会显式处理手动实例化的类型。有关详细信息，请参阅有关Disposal of Services的ASP.NET核心文档。

Answer 2

您可以使用：

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

依赖注入：ActivatorUtilities将向您的类注入任何依赖。

Answer 3

如果构造函数还具有应由DI解决的依赖关系，则可以使用：

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>()));

Answer 4

您可以像下面那样使用。试图用一个例子来解释。

经理班。

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

Startup.cs类

        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);
        });
    }

您可以在此处阅读完整的示例。

DI in Startup.cs in .Net Core

Answer 5

晚了一点，但是您可以直接注入一个工厂来创建并公开提供程序类的实例。

依赖注入，使用参数

5 个答案: