如何在启动时启动服务（`IServiceCollection`）

Question

我想在启动时运行一个单件服务，而不是等待某些Controller通过依赖注入构建服务。

该服务处理来自服务总线的数据，似乎不依赖于客户端流量。初始化它的最简洁方法是什么？

Answer 1

通常您会正常实例化服务，然后将其引用传递给AddSingleton()方法。

var someRepository = new SomeRepository(/*pass in configuration and dependencies*/);

// pass instance of the already instantiated service
services.AddSingleton<ISomeRespository>(someRepository);

修改

或热身扩展方法：

public static class WarmupServiceProviderExtensions
{
    public static void WarmUp(this IServiceProvider app)
    {
        // Just call it to resolve, no need to safe a reference
        app.RequestService<ISomeRepository>();
    }
}

并在你的Startup.cs中

public void Configure(IServiceProvider app) 
{
    app.UseXyz(...);

    // warmup/initailize your services
    app.WarmUp();
}

Answer 2

哦，即使您不需要配置它，也只需在Startup.cs中引用它。

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // Has message bus connection
    services.AddSingleton<ISomeRespository, SomeRepository>();

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(... ISomeRespository db)
{

Duh：）