如何将范围服务注入DbContext？ 网络核心

Question

I am building the multi tenant app and trying to get the data security working now. Unit tests of Context are working nice because I create the context with options and UserContext, but I am struggling to get it working in assembly as it needs userContext to be injected.

I cannot use standard controller injection as with everything else, as if I have it, the context creation fails:

services.AddEntityFrameworkNpgsql()
                .AddDbContext<MultiTenantContext>(o =>
                    o.UseNpgsql(Configuration.GetConnectionString("DbContext")

I cannot or I do not know how to inject my UserContext this way...

Answer 1

Simple use constructor injection. It is working the same way like in a controller.

public class MultiTenantContext : DbContext
{
    private UserContext _userContext;

    public MultiTenantContext(DbContextOptions options, UserContext userContext) : base(options)
    {
        _userContext = userContext;
    }
}

You need to make sure, that you register the UserContext service before you are registering the entity framework. eg

services.AddScoped<UserContext, UserContext>();
services.AddEntityFrameworkNpgsql()
                .AddDbContext<MultiTenantContext>(o =>
                    o.UseNpgsql(Configuration.GetConnectionString("DbContext")

Answer 2

I am assuming for multi-tenant application you are trying to find out Tenant based on logged in user from HttpRequest. You can do something like this

public class UserContext
{
    private readonly IHttpContextAccessor _accessor;
    public RequestContextAdapter(IHttpContextAccessor accessor)
    {
        this._accessor = accessor;
    }

    public string UserID
    {
        get
        {
            // you have access to HttpRequest object here
            //this._accessor.HttpContext.Request
        }
    }
}

ASP.NET Core will automatically inject IHttpContextAccessor into UserContext

You also have to register UserContext

services.AddScoped<UserContext, UserContext>();

then use constructor injection to inject UserContext wherever you need

Answer 3

The accepted answer didn't work for me as well, I ended up doing a very similar approach to the original answer, thanks @Christian for your guidance.

I wanted to inject a service into the DbContext which is responsible to load connection string dynamically based on some HTTP request header below is the code used

In Startup:

  services.AddScoped<IConnectionService, ConnectionService>();
  services.AddDbContext<MyDbContext>(); //Connection string will be set on event OnConfiguring

In MyDbContext:

public class MyDbContext : DbContext
    {
        private readonly IConnectionService _connectionService;

        public MyDbContext(DbContextOptions<MyDbContext> options, IConnectionService connectionService) : base(options)
        {
            _connectionService = connectionService;
        }

        public DbSet<Customer> Customers { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            var connectionString = _companyConnectionService.ConnectionString; //Custom logic to read from http request header certain value and switch connection string
            optionsBuilder.UseSqlServer(connectionString);
        }
    }

Hope this will help.