无法访问已处理的对象。此错误的原因 - 与依赖注入相关的 Asp.net Core 异常

Question

I am trying to perform some database operation on receiving the message from Azure service bus.

I am calling my service and my service internally calls a repository to access db get data and return, but I am getting a System.ObjectDisposedException Exception message on using the context object to access my db.

Please guide me through this?

startup.cs

public Startup(IConfiguration configuration) 
{
    Configuration = configuration;
}

public IConfiguration Configuration 
{
    get;
}

public static string clientId 
{
    get;
    private set;
}

public static string clientSecret 
{
    get;
    private set;
}
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services) 
{
    string azureConnectionString = Configuration["ConnectionStrings:DefaultConnection"];

    services.AddControllers();
    clientId = Configuration.GetSection("fuelSDK").GetSection("clientId").Value;
    clientSecret = Configuration.GetSection("fuelSDK").GetSection("clientSecret").Value;

    var dbUtils = new AzureDatabaseUtils();
    var sqlConnection = dbUtils.GetSqlConnection(azureConnectionString);

    services.AddDbContext < DeciemStoreContext > (options = >options.UseSqlServer(sqlConnection));

    #region RegisterServices

    services.AddTransient < IServiceBusConsumer,
    ServiceBusConsumer > ();
    services.AddTransient < IOrderRepository,
    OrderRepository > ();
    services.AddTransient < IOrderService,
    OrderService > ();

    #endregion

    Configuration.GetSection("Global").Get < Global > ();
}

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env) 
{
    if (env.IsDevelopment()) 
    {
        app.UseDeveloperExceptionPage();
    }

    #region Azure ServiceBus
    using(var scope = app.ApplicationServices.CreateScope()) 
    {
        var bus = scope.ServiceProvider.GetService < IServiceBusConsumer > ();
        bus.RegisterOnMessageHandlerAndReceiveMessages();

    }

    #endregion

    app.UseRouting();

    app.UseAuthorization();

    app.UseEndpoints(endpoints = > {
        endpoints.MapControllerRoute("api", "api/{controller}/{action}/{id?}");
    });
}

MessageConsumerClass.cs

public interface IServiceBusConsumer 
{
    void RegisterOnMessageHandlerAndReceiveMessages();
    Task CloseQueueAsync();
}

public class ServiceBusConsumer: IServiceBusConsumer 
{
    private IOrderService _orderService;
    private readonly ILogger _logger;

    static ISubscriptionClient subscriptionClient;

    public ServiceBusConsumer(ILogger < ServiceBusConsumer > logger, IOrderService orderService) 
    {
        _logger = logger;
        _orderService = orderService;
        const string ServiceBusConnectionString = "Endpoint=sb://qa10em.servicebus.windows.net/;SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=v2sIQi/2fY2rENS7trnFd38m2wqNJKuWYMFJxWccK8E=";
        const string TopicName = "businessoperation";
        const string SubscriptionName = "SFOperation_sub";

        //SubscriberCreateAsync().Wait();
        subscriptionClient = new SubscriptionClient(ServiceBusConnectionString, TopicName, SubscriptionName);
    }

    public void RegisterOnMessageHandlerAndReceiveMessages()
    {
        var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler) {
            MaxConcurrentCalls = 1,
            AutoComplete = false
        };
        subscriptionClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions);
    }

    private async Task ProcessMessagesAsync(Message message, CancellationToken token) 
    {
        try 
        {
            Console.WriteLine($ "Received message: SequenceNumber:{message.SystemProperties.SequenceNumber} Body:{Encoding.UTF8.GetString(message.Body)}");

            var mb = JsonConvert.DeserializeObject < MessageBody > (Encoding.UTF8.GetString(message.Body));

            if (mb != null) 
            {
                Global.Entity = mb.Entity;
                Global.ActionName = mb.ActionName;
                Global.Value = mb.Value;
            }
            else 
            {
                Global.Entity = "";
                Global.ActionName = "";
                Global.Value = "";
            }
            await subscriptionClient.CompleteAsync(message.SystemProperties.LockToken);

            //Here I am calling the service to get data
            var orders = _orderService.GetByOrderId(Global.Value);
            //await _orderService.GetByOrderId(Global.Value);
        }
        catch(Exception ex) 
        {
            throw ex;
        }
    }

OrderRepository.cs -- Here in this file I am receiving the DBContext disposed exception

protected DeciemStoreContext _context;
public OrderRepository(DeciemStoreContext context) 
{
    _context = context;
}

public async Task <IEnumerable<Order>> ListAsync() 
{
    return await _context.Order.ToListAsync();
}

public async Task <List<Order>> GetByOrderId(string OrderId) 
{
    try 
    {
        int oid = Convert.ToInt32(OrderId);
        // here while trying to access _context the context seems to have disposed before 
        var order = from o in _context.Order
        where o.OrderId == oid
        orderby o.OrderId
        select new Order 
        {
            OrderId = o.OrderId,
            CustomerId = o.CustomerId,
            ProductSubtotal = o.ProductSubtotal,
            PreTaxSubtotal = o.PreTaxSubtotal,
            DiscountCode = o.DiscountCode,
            DiscountPercent = o.DiscountPercent,
            DiscountAmount = o.DiscountAmount,
            GrandTotal = o.GrandTotal,
            Ponumber = o.Ponumber,
            PostedDate = o.PostedDate
        };

        return await order.ToListAsync();
    }
    catch(Exception ex) 
    {
        throw ex;
    }
}

Answer 1

Look at this line

services.AddTransient<IServiceBusConsumer, ServiceBusConsumer>();

here you create a new consumer for each time they are requested (at least once per request). This means that you open the ServiceBus connection and close it each time when ServiceBusConsumer created.

Service Bus client objects, such as QueueClient or MessageSender, are created through a MessagingFactory object, which also provides internal management of connections.

It is recommended that you do not close messaging factories or queue, topic, and subscription clients after you send a message, and then re-create them when you send the next message. Closing a messaging factory deletes the connection to the Service Bus service, and a new connection is established when recreating the factory. Establishing a connection is an expensive operation that you can avoid by reusing the same factory and client objects for multiple operations. You can safely use these client objects for concurrent asynchronous operations and from multiple threads.

See Best Practices for performance improvements using Service Bus Messaging

So, to fix that try to register it as a singleton

services.AddSingleton<IServiceBusConsumer, ServiceBusConsumer>();