ASP.NET Core 2.2 How to add two constructors to the same class using dependency injection? - entity-framework

Question

I have a class "ConnectorManagement" in which I need to use both SignalR services as well as querying a db table using EF CORE.
I cant work out how to load both dbcontext and hubcontext into the same class using a constructor and dependancy injection. The current result is visual studio fails to load the project when run in debug. Tried researching this but not understanding what needs to be done.
Current code below:
namespace myNamespace.Controller
{
public class ConnectorManagement : IHostedService
{
private static readonly log4net.ILog log = log4net.LogManager.GetLogger(typeof(Logger));
private readonly IHubContext<MessageHub> _hubContext;
public readonly ApplicationDbContext _context;
public ConnectorManagement(IHubContext<MessageHub> hubContext, ApplicationDbContext context)
{
_hubContext = hubContext;
_context = context;
}
public Task StartAsync(CancellationToken cancellationToken)
{
log.Info("Initial Test");
return Task.CompletedTask;
}
public Task StopAsync(CancellationToken cancellationToken)
{
throw new NotImplementedException();
}
dbcontext class:
namespace myNamespace.Data
{
public class ApplicationDbContext : IdentityDbContext
{
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
: base(options)
{
}
public DbSet<myProject.Models.ConnectorInbound> ConnectorInbound { get; set; }
public DbSet<myProject.Models.ConnectorOutbound> ConnectorOutbound { get; set; }
public DbSet<myProject.Models.SystemMapping> SystemMapping { get; set; }
}
}
startup class:
namespace myProjectNamespace
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.Configure<CookiePolicyOptions>(options =>
{
// This lambda determines whether user consent for non-essential cookies is needed for a given request.
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(
Configuration.GetConnectionString("DefaultConnection")));
services.AddDefaultIdentity<IdentityUser>()
.AddDefaultUI(UIFramework.Bootstrap4)
.AddEntityFrameworkStores<ApplicationDbContext>();
// Start up the TcpServerTcpServer engine
services.AddHostedService<ConnectorManagement>();
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
services.AddSignalR();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
app.UseDatabaseErrorPage();
}
else
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();
app.UseAuthentication();
app.UseSignalR(routes =>
{
routes.MapHub<MessageHub>("/messageHub");
});
loggerFactory.AddLog4Net();
app.UseMvc();
}
}
}

Answer 1

I wasn't paying attention to the fact that you're injecting this into a hosted service. Hosted services are singletons and both the hub context and database context are scoped services. You need to inject IServiceProvider instead and then create a scope. This will need to be done for every usage; you cannot persist it on an ivar, for example. You can only use it within the using statement.
using (var scope = _serviceProvider.CreateScope())
{
var context = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
// Do something
}