Restructured project.

Backend.cs

@@ -1,5 +1,6 @@
 using Backend.DatabaseHandler;
 using Backend.ServiceHander;
+using Backend.Interface;
 using Microsoft.AspNetCore.HttpOverrides;
 
 var builder = WebApplication.CreateBuilder(args);

Controller/MarketDataController.cs

@@ -2,7 +2,7 @@ using Backend.ServiceHander;
 using Backend.MarketDataRequest;
 using Microsoft.AspNetCore.Mvc;
 
-namespace BackendApi.Controller
+namespace Backend.Controller
 {
 	[ApiController]
 	[Route("api/market")]

Controller/UserInterestController.cs

@@ -1,9 +1,10 @@
 using Backend.DatabaseHandler;
-using Backend.UserInterests;
+using Backend.ServiceHander;
+using Backend.Interface;
 using Microsoft.AspNetCore.Mvc;
 
-namespace Backend.Controllers;
+namespace Backend.Controllers
-
+{
 	[ApiController]
 	[Route("api/user-interest")]
 	public sealed class UserInterestController : ControllerBase
@@ -64,3 +65,4 @@ public sealed class UserInterestController : ControllerBase
 			}
 		}
 	}
+}

DatabaseHandler/IUserInterestCache.cs

@@ -1,8 +0,0 @@
-namespace Backend.DatabaseHandler;
-
-public interface IUserInterestStore
-{
-	Task<List<string>> FetchAllAsync(string user, string type);
-	Task<bool> AddAsync(string user, string type, string value);
-	Task<bool> RemoveAsync(string user, string type, string value);
-}

DatabaseHandler/PostgresHistoricalMarketDataStore.cs

@@ -1,4 +1,5 @@
 using Backend.MarketDataRequest;
+using Backend.Interface;
 using Npgsql;
 
 namespace Backend.DatabaseHandler

DatabaseHandler/PostgresUserInterestStore.cs

@@ -1,4 +1,5 @@
 using Npgsql;
+using Backend.Interface;
 
 namespace Backend.DatabaseHandler;
 

Interface/IHistoricalMarketDataCache.cs

@@ -1,6 +1,7 @@
 using Backend.MarketDataRequest;
+using Backend.DatabaseHandler;
 
-namespace Backend.DatabaseHandler
+namespace Backend.Interface
 {
 	public interface IHistoricalMarketDataCache
 	{

Interface/IUserInterestCache.cs

@@ -0,0 +1,9 @@
+namespace Backend.Interface
+{
+	public interface IUserInterestStore
+	{
+		Task<List<string>> FetchAllAsync(string user, string type);
+		Task<bool> AddAsync(string user, string type, string value);
+		Task<bool> RemoveAsync(string user, string type, string value);
+	}
+}

MarketDataRequest/IBGatewayControl.cs

@@ -131,6 +131,7 @@ namespace Backend.MarketDataRequest
 
 			Console.WriteLine($"[error] id={id}, code={errorCode}, time={errorTime}, msg={errorMsg}");
 
+			// Live requests
 			if (id > 0 && _liveRequests.TryRemove(id, out var liveTcs))
 			{
 				Client.cancelMktData(id);
@@ -141,6 +142,7 @@ namespace Backend.MarketDataRequest
 				return;
 			}
 
+			// Historical requests
 			if (id > 0 && _historyRequests.TryRemove(id, out var historyTcs))
 			{
 				_BarsByRequest.TryRemove(id, out _);
@@ -150,6 +152,7 @@ namespace Backend.MarketDataRequest
 				return;
 			}
 
+			// Fundamentals
 			if (id > 0 && _fundamentalsRequests.TryRemove(id, out var fundamentalsTcs))
 			{
 				Client.cancelMktData(id);

ServiceHandler/MarketDataHander.cs

@@ -1,5 +1,6 @@
 using Backend.DatabaseHandler;
 using Backend.MarketDataRequest;
+using Backend.Interface;
 using IBApi;
 using System.Globalization;
 

ServiceHandler/UserInterestsHandler.cs

@@ -0,0 +1,25 @@
+namespace Backend.ServiceHander
+{
+	public sealed class UserInterestFetchRequest
+	{
+		public string User { get; set; } = string.Empty;
+		public string Type { get; set; } = string.Empty; // "symbol" or "topic"
+	}
+
+	public sealed class UserInterestModifyRequest
+	{
+		public string User { get; set; } = string.Empty;
+		public string Type { get; set; } = string.Empty; // "symbol" or "topic"
+		public string Value { get; set; } = string.Empty; // symbol or topic
+	}
+
+	public sealed class UserInterestFetchResponse
+	{
+		public List<string> Items { get; set; } = new();
+	}
+
+	public sealed class BoolResponse
+	{
+		public bool Success { get; set; }
+	}
+}

UserInterests/UserInterests.cs

@@ -1,24 +0,0 @@
-namespace Backend.UserInterests;
-
-public sealed class UserInterestFetchRequest
-{
-	public string User { get; set; } = string.Empty;
-	public string Type { get; set; } = string.Empty; // "symbol" or "topic"
-}
-
-public sealed class UserInterestModifyRequest
-{
-	public string User { get; set; } = string.Empty;
-	public string Type { get; set; } = string.Empty; // "symbol" or "topic"
-	public string Value { get; set; } = string.Empty; // symbol or topic
-}
-
-public sealed class UserInterestFetchResponse
-{
-	public List<string> Items { get; set; } = new();
-}
-
-public sealed class BoolResponse
-{
-	public bool Success { get; set; }
-}