C#在 .NET中使用依赖注入的示例详解

using Microsoft.Extensions.DependencyInjection;
 
namespace ConsoleDI.Example;
 
public interface IReportServiceLifetime
{
    Guid Id { get; }
 
    ServiceLifetime Lifetime { get; }
}
 
// 创建了多个接口和相应的实现。 其中每个服务都唯一标识并与 ServiceLifetime 配对
public interface IExampleTransientService : IReportServiceLifetime
{
    ServiceLifetime IReportServiceLifetime.Lifetime => ServiceLifetime.Transient;
}
 
public interface IExampleScopedService : IReportServiceLifetime
{
    ServiceLifetime IReportServiceLifetime.Lifetime => ServiceLifetime.Scoped;
}
 
public interface IExampleSingletonService : IReportServiceLifetime
{
    ServiceLifetime IReportServiceLifetime.Lifetime => ServiceLifetime.Singleton;
}
 
internal sealed class ExampleTransientService : IExampleTransientService
{
    Guid IReportServiceLifetime.Id { get; } = Guid.NewGuid();
}
 
internal sealed class ExampleScopedService : IExampleScopedService
{
    Guid IReportServiceLifetime.Id { get; } = Guid.NewGuid();
}
 
internal sealed class ExampleSingletonService : IExampleSingletonService
{
    Guid IReportServiceLifetime.Id { get; } = Guid.NewGuid();
}

namespace ConsoleDI.Example;
 
internal sealed class ServiceLifetimeReporter(
    IExampleTransientService transientService,
    IExampleScopedService scopedService,
    IExampleSingletonService singletonService)
{
    public void ReportServiceLifetimeDetails(string lifetimeDetails)
    {
        Console.WriteLine(lifetimeDetails);
 
        LogService(transientService, "每次都是新建的对象，一直保持不同");
        LogService(scopedService, "在函数域范围内只创建一次，不同函数内为不同对象");
        LogService(singletonService, "全局单例，一直是同一个");
    }
 
    private static void LogService<T>(T service, string message)
        where T : IReportServiceLifetime =>
        Console.WriteLine($"    {typeof(T).Name}: {service.Id} ({message})");
}