Add SignalR integration for real-time weather updates

Implemented SignalR to enable real-time communication between the server and connected clients. Added a new hub (`WeatherUpdateHub`), a background service (`SignalRSendService`), and modified both the API backend and React frontend for seamless message broadcasting and handling.

Api/Api.csproj

@@ -8,6 +8,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="9.0.0" />
+    <PackageReference Include="Microsoft.AspNetCore.SignalR" Version="1.2.0" />
     <PackageReference Include="NSwag.AspNetCore" Version="14.2.0" />
   </ItemGroup>
 

Api/Program.cs

@@ -1,9 +1,13 @@
+using Api.SignalR;
+
 var builder = WebApplication.CreateBuilder(args);
 
 // Add services to the container.
 // Learn more about configuring OpenAPI at https://aka.ms/aspnet/openapi
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddOpenApi();
+builder.Services.AddSignalR();
+builder.Services.AddHostedService<SignalRSendService>();
 builder.Services.AddOpenApiDocument(config =>
 {
     config.Title = "NSwag Demo API";
@@ -12,9 +16,10 @@ builder.Services.AddCors(options =>
 {
     options.AddDefaultPolicy(policy =>
     {
-        policy.AllowAnyOrigin()
+        policy.WithOrigins("http://localhost:3000") // Specify the allowed origin
               .AllowAnyHeader()
-              .AllowAnyMethod();
+              .AllowAnyMethod()
+              .AllowCredentials(); // Allow credentials
     });
 });
 
@@ -36,7 +41,7 @@ var summaries = new[]
     "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
 };
 
-app.MapGet("/weatherforecast", () =>
+app.MapGet("/weatherforecast", async () =>
 {
     var forecast =  Enumerable.Range(1, 5).Select(index =>
         new WeatherForecast
@@ -46,10 +51,15 @@ app.MapGet("/weatherforecast", () =>
             summaries[Random.Shared.Next(summaries.Length)]
         ))
         .ToArray();
+
     return forecast;
 })
 .WithName("GetWeatherForecast");
 
+
+// Add SignalR hub
+app.MapHub<WeatherUpdateHub>("/WeatherUpdateHub");
+
 app.Run();
 
 record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)

Api/SignalR/SignalRSendService.cs

@@ -0,0 +1,31 @@
+using Microsoft.AspNetCore.SignalR;
+
+namespace Api.SignalR
+{
+    public class SignalRSendService(IHubContext<WeatherUpdateHub> hubContext, ILogger<SignalRSendService> logger) : BackgroundService
+    {
+        
+        #region Override ExecuteAsync
+
+        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+        {
+            while (!stoppingToken.IsCancellationRequested)
+            {
+                // For example, wait 10 seconds between messages.
+                await Task.Delay(TimeSpan.FromSeconds(10), stoppingToken);
+
+                // Log or do any work here.
+                logger.LogInformation("Background service sending message at: {Time}", DateTime.Now);
+
+                // Send a message to all connected clients.
+                await hubContext.Clients.All.SendAsync(
+                    "ReceiveMessage", // This is the client method name.
+                    "Background Service", // Example sender.
+                    "Hello from the background task!", // The message.
+                    stoppingToken);
+            }
+        }
+
+        #endregion
+    }
+}

Api/SignalR/WeatherUpdateHub.cs

@@ -0,0 +1,14 @@
+using Microsoft.AspNetCore.SignalR;
+
+namespace Api.SignalR
+{
+    public class WeatherUpdateHub: Hub
+    {
+        // This method can be called by connected clients.
+        public async Task SendMessage(string user, string message)
+        {
+            // Broadcast the message to all connected clients.
+            await Clients.All.SendAsync("ReceiveMessage", user, message);
+        }
+    }
+}