依赖注入,注入参数

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...
}

和服务注册:

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"));

Answer 2

如果构造函数还具有应由 DI 解析的依赖项，则可以使用它：

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...
}

启动.cs：

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

Answer 3

您可以使用类似于下面示例代码的内容。

经理类：

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示例：.Net Core 中 Startup.cs 中的 DI

Answer 4

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项。