SignalR getting disconnected while applying Dependency Injection - asp.net-core

Question

I am new to SignalR and building a live chat by using .NET 5 and angular 13. While establishing the connection it is giving this error-- Connection closed with an error. NullReferenceException
After multiple debagging I found out what is the root cause of the problem. When I inject any dependency to my message hub. NullReferenceException error is happened. without dependency the connection is established properly.
here is my MessageHub.cs code (with dependency)
public class MessageHub : Hub
{
private readonly IMessageRepository _messageRepository;
private readonly IUserRepository _userRepository;
public MessageHub(IMessageRepository messageRepository, IUserRepository userRepository)
{
_messageRepository = messageRepository;
_userRepository = userRepository;
}
public override async Task OnConnectedAsync()
{
var httpContext = Context.GetHttpContext();
var otherUser = httpContext.Request.Query["user"].ToString();
var groupName = GetGroupName(Context.User.GetUsername(), otherUser);
await Groups.AddToGroupAsync(Context.ConnectionId, groupName);
}
public override async Task OnDisconnectedAsync(Exception exception)
{
await base.OnDisconnectedAsync(exception);
}
}
Startup.cs (ConfigureServices)
services.AddSignalR(e=>
{
e.EnableDetailedErrors = true;
});
Startup.cs (Configure)
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
endpoints.MapHub<MessageHub>("hubs/message");
});
I extremely need this dependency to complete my functionality. I got stack with this. If I remove the Dependency it works fine. I tried to find some solution from various sources but didn't work for me. if anyone help me. I will be really appreciate for this.

Answer 1

After doing some study, a solution I applied that worked for me. We Can Retrieve service object. so in startup.cs what I did given below
Startup.cs (ConfigureServices)
//we can retrieve service object
public static IServiceProvider serviceProvider;
services.AddSignalR()
services.AddScoped<IUserRepository, UserRepository>();
services.AddScoped<IMessageRepository, MessageRepository>();
In my MessageHub.cs instead of using Dependency Injection I Retrieve Required Service and define it in the filed like below
MessageHub.cs
public class MessageHub : Hub
{
private readonly IMessageRepository _messageRepository;
private readonly IUserRepository _userRepository;
public MessageHub()
{
_messageRepository = (IMessageRepository)Startup.serviceProvider.GetRequiredService(typeof(IMessageRepository));
_userRepository = (IUserRepository)Startup.serviceProvider.GetRequiredService(typeof(IUserRepository));
}
// other code....
}
It worked for me. Now I can implement my necessary method from IRepository and SignalR also working properly.