How to inject dependencies inside a custom checker?

[lmcarreiro]

In the example:

public void ConfigureServices(IServiceCollection services)
{
    //...
    services
        .AddHealthChecks()
        .AddCheck(new SqlConnectionHealthCheck("MyDatabase", Configuration["ConnectionStrings:DefaultConnection"]));
    //...
}

public void Configure(IApplicationBuilder app)
{
    app.UseHealthChecks("/healthz");
}

I could add custom checks that implement the Microsoft.Extensions.Diagnostics.HealthChecks.IHealthCheck interface. But since I need to provide to the AddCheck method an instance instead of a type, and it needs to run inside the ConfigureServices method, I can't inject any dependency in my custom checker.

Is there any way to workaround this?

[davidfowl]

cc @rynowak

[jasonwadsworth]

The best work around I’ve come up with so far is to have a constructor that takes an IServiceCollection and pass the services object into your class. From there you can build an IServiceProvider and you can get your services from there. The downside to this is that you need to be sure all your DI dependencies are added before you do this.

[JuergenGutsch]

The interface of AddCheck isn't the best one. and could be more generic in the future:

services.AddCheck<SqlConnectionHealthCheck, SqlConnectionHealthCheckOptions>()
services.AddCheck<SqlConnectionHealthCheck, SqlConnectionHealthCheckOptions>(new SqlConnectionHealthCheckOptions())
services.AddCheck<SqlConnectionHealthCheck, SqlConnectionHealthCheckOptions>(options => {})

[lmcarreiro]

My question was answered here: https://stackoverflow.com/a/52029647/4871582

But I agree with @JuergenGutsch, the interface of AddCheck could be better.

[lmcarreiro]

We're making changes in preview2 that allow you to register health checks with any DI lifetime. You'll also be able to register health checks like builder.AddHealthCheck<T>

Closing this issue based on this comment from @rynowak in https://github.com/aspnet/Diagnostics/issues/464#issuecomment-416729281