Impossible to use dependency injection in an Hangfire job

Question

Context

I use Hangfire (version 1.7.11) as a scheduler. But I can't use proper DI in my jobs.

What works so far

I have no problem scheduling something like this, given the fact SomeConcreteService have a parameterless constructor:

RecurringJob.AddOrUpdate<SomeConcreteService>(jobId, mc => Console.WriteLine(
    $"Message from job: {mc.GetValue()}"), "1/2 * * * *");

What does not work

But I get an exception when I try to inject a service into a Hangfire job using what is recommended here: https://docs.hangfire.io/en/latest/background-methods/using-ioc-containers.html

When I try to add a new scheduled job using DI, I get the following exception:

Exception thrown: 'System.InvalidOperationException' in System.Linq.Expressions.dll: 'variable 'mc' of type 'TestHangfire.IMyContract' referenced from scope '', but it is not defined'

The exception occurs a this line:

RecurringJob.AddOrUpdate<IMyContract>(jobId, mc => Console.WriteLine(
    $"Message from job {jobId} => {mc.GetValue()}"), "1/2 * * * *");

The problem is so trivial that I am sure I am missing something obvious.

Thanks for helping.

The (nearly) full code

Service:

public interface IMyContract
{
    string GetValue();
}

public class MyContractImplementation : IMyContract
{
    public string _label;

    public MyContractImplementation(string label)
    {
        _label = label;
    }

    public string GetValue() => $"{_label}:{Guid.NewGuid()}";
}

2 kinds of activators:

public class ContainerJobActivator : JobActivator
{
    private IServiceProvider _container;

    public ContainerJobActivator(IServiceProvider serviceProvider) =>
        _container = serviceProvider;

    public override object ActivateJob(Type type) => _container.GetService(type);
}

public class ScopedContainerJobActivator : JobActivator
{
    readonly IServiceScopeFactory _serviceScopeFactory;
    public ScopedContainerJobActivator(IServiceProvider serviceProvider)
    {
        _serviceScopeFactory = serviceProvider.GetService<IServiceScopeFactory>();
    }

    public override JobActivatorScope BeginScope(JobActivatorContext context) =>
        new ServiceJobActivatorScope(_serviceScopeFactory.CreateScope());

    private class ServiceJobActivatorScope : JobActivatorScope
    {
        readonly IServiceScope _serviceScope;
        public ServiceJobActivatorScope(IServiceScope serviceScope) =>
            _serviceScope = serviceScope;

        public override object Resolve(Type type) =>
            _serviceScope.ServiceProvider.GetService(type);
    }
}

Startup:

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddHangfire(configuration => configuration
            .SetDataCompatibilityLevel(CompatibilityLevel.Version_170)
            .UseSimpleAssemblyNameTypeSerializer()
            .UseRecommendedSerializerSettings()
            .UseSqlServerStorage("connection string", new SqlServerStorageOptions
            {
                CommandBatchMaxTimeout = TimeSpan.FromMinutes(5),
                SlidingInvisibilityTimeout = TimeSpan.FromMinutes(5),
                QueuePollInterval = TimeSpan.Zero,
                UseRecommendedIsolationLevel = true,
                UsePageLocksOnDequeue = true,
                DisableGlobalLocks = true
            }));

        services.AddHangfireServer();
        services.BuildServiceProvider();
        services.AddScoped<IMyContract>(i => new MyContractImplementation("blabla"));
        // doesn't work either
        // services.AddSingleton<IMyContract>(i => new MyContractImplementation("blabla"));
        // doesn't work either
        // services.AddTransient<IMyContract>(i => new MyContractImplementation("blabla"));

    }

    public void Configure(
        IApplicationBuilder app, 
        IWebHostEnvironment env,
        IServiceProvider serviceProvider)
    {
        // Just to ensure the service is correctly injected...
        Console.WriteLine(serviceProvider.GetService<IMyContract>().GetValue());

        // I face the problem for both activators: ScopedContainerJobActivator or ContainerJobActivator
        GlobalConfiguration.Configuration.UseActivator(new ContainerJobActivator(serviceProvider));
        // GlobalConfiguration.Configuration.UseActivator(new ScopedContainerJobActivator(serviceProvider));

        app.UseRouting();
        app.UseHangfireDashboard();

        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        app.UseEndpoints(endpoints =>
        {
            endpoints.MapGet("/", async context =>
            {
                await context.Response.WriteAsync(
                    JsonSerializer.Serialize(
                        Hangfire.JobStorage.Current.GetConnection().GetRecurringJobs()
                    .Select(i => new { i.Id, i.CreatedAt, i.Cron }).ToList()));
            });
            endpoints.MapGet("/add", async context =>
            {
                var manager = new RecurringJobManager();
                var jobId = $"{Guid.NewGuid()}";

                // I GET AN EXCEPTION HERE: 
                // Exception thrown: 'System.InvalidOperationException' in System.Linq.Expressions.dll: 'variable 'mc' of type 'TestHangfire.IMyContract' referenced from scope '', but it is not defined'
                manager.AddOrUpdate<IMyContract>(jobId, mc => Console.WriteLine(
                    $"Message from job {jobId} => {mc.GetValue()}"), "1/2 * * * *");

                // doesn't work either: it's normal, it is just a wrapper of what is above
                // RecurringJob.AddOrUpdate<IMyContract>(jobId, mc => Console.WriteLine($"Message from job {jobId} => {mc.GetValue()}"), "1/2 * * * *");

                await context.Response.WriteAsync($"Schedule added: {jobId}");
            });
        });
    }
}

Answer 1

I found the issue.

As it was actually the expression that seemed to cause an issue, and given the fact that the other way to add a recurring job is to transmit a type, and a method info, it seemed to me that the problem was caused by an expression that was too evolved. So I changed the approach to have a method of my service that make the whole job by being given a parameter.

Here is the new code that works:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Hangfire;
using Hangfire.SqlServer;
using Hangfire.Storage;
using System.Text.Json;

namespace TestHangfire
{
    #region Service
    public interface IMyContract
    {
        void MakeAction(string someText);
    }
    public class MyContractImplementation : IMyContract
    {
        public string _label;

        public MyContractImplementation(string label)
        {
            _label = label;
        }

        public void MakeAction(string someText) => Console.WriteLine($"{_label}:{someText}");
    }
    #endregion

    #region 2 kinds of activators
    public class ContainerJobActivator : JobActivator
    {
        private IServiceProvider _container;

        public ContainerJobActivator(IServiceProvider serviceProvider)
        {
            _container = serviceProvider;
        }

        public override object ActivateJob(Type type)
        {
            return _container.GetService(type);
        }
    }
    #endregion
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddHangfire(configuration => configuration
                .SetDataCompatibilityLevel(CompatibilityLevel.Version_170)
                .UseSimpleAssemblyNameTypeSerializer()
                .UseRecommendedSerializerSettings()
                .UseSqlServerStorage("Server=localhost,1433;Database=HangfireTest;user=sa;password=xxxxxx;MultipleActiveResultSets=True", new SqlServerStorageOptions
                {
                    CommandBatchMaxTimeout = TimeSpan.FromMinutes(5),
                    SlidingInvisibilityTimeout = TimeSpan.FromMinutes(5),
                    QueuePollInterval = TimeSpan.Zero,
                    UseRecommendedIsolationLevel = true,
                    UsePageLocksOnDequeue = true,
                    DisableGlobalLocks = true
                }));

            services.AddHangfireServer();
            services.BuildServiceProvider();
            services.AddTransient<IMyContract>(i => new MyContractImplementation("blabla"));
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IServiceProvider serviceProvider)
        {
            GlobalConfiguration.Configuration.UseActivator(new ContainerJobActivator(serviceProvider));

            app.UseRouting();
            app.UseHangfireDashboard();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapGet("/", async context =>
                {
                    await context.Response.WriteAsync(JsonSerializer.Serialize(Hangfire.JobStorage.Current.GetConnection().GetRecurringJobs()
                        .Select(i => new { i.Id, i.CreatedAt, i.Cron }).ToList()));
                });
                endpoints.MapGet("/add", async context =>
                {
                    var manager = new RecurringJobManager();
                    var jobId = $"{Guid.NewGuid()}";
                    manager.AddOrUpdate<IMyContract>(jobId, (IMyContract mc) => mc.MakeAction(jobId), "1/2 * * * *");

                    await context.Response.WriteAsync($"Schedule added: {jobId}");
                });
            });
        }
    }
}