Implemented Tenant Identification Service to dynamically resolve database connection strings based on 'X-Client-ID' header

ContextMiddleware/ConnectionStringMiddleware.cs

@@ -0,0 +1,41 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Configuration;
+using System.Threading.Tasks;
+
+namespace TodoApi.ContextMiddleware
+{
+    public class ConnectionStringMiddleware
+    {
+        private readonly RequestDelegate _next;
+        private readonly IConfiguration _configuration;
+
+        public ConnectionStringMiddleware(RequestDelegate next, IConfiguration configuration)
+        {
+            _next = next;
+            _configuration = configuration;
+        }
+
+        public async Task InvokeAsync(HttpContext context)
+        {
+            // Extract the client identifier
+            var clientId = context.Request.Headers["X-Client-ID"].ToString();
+
+            if (string.IsNullOrEmpty(clientId) ||
+                !_configuration.GetSection("ConnectionStrings:ClientDatabases").Exists())
+            {
+                context.Response.StatusCode = 400; // Bad Request
+                await context.Response.WriteAsync("Invalid or missing client ID.");
+                return;
+            }
+
+            // Retrieve the connection string
+            var connectionString = _configuration.GetSection($"ConnectionStrings:ClientDatabases:{clientId}").Value;
+
+            // Store the connection string in the HttpContext for downstream services
+            context.Items["ConnectionString"] = connectionString;
+
+            await _next(context);
+        }
+    }
+
+}

Controllers/TodoController.cs

@@ -16,23 +16,33 @@ namespace TodoApi.Controllers
     public class TodoController : Controller
     {
         private readonly TodoContext _context;
-
-        public TodoController(TodoContext context)
+        private readonly DynamicDbContextFactory _dbContextFactory;
+        private readonly TodoContext _contextDynamic;
+        public TodoController(TodoContext context, DynamicDbContextFactory dbContextFactory)
         {
             _context = context;
-
+           
             if (_context.TodoItems.Count() == 0)
             {
                 _context.TodoItems.Add(new TodoItem { Name = "Item1" });
                 _context.SaveChanges();
             }
+
+            _dbContextFactory = dbContextFactory;
+            _contextDynamic = _dbContextFactory.CreateDbContext();
+            if (_contextDynamic.TodoItems.Count() == 0)
+            {
+                _contextDynamic.TodoItems.Add(new TodoItem { Name = "Item1" });
+                _contextDynamic.SaveChanges();
+            }
         }
 
         // GET: api/Todo
         [HttpGet]
         public async Task<ActionResult<IEnumerable<TodoItem>>> GetTodoItem()
         {
-            return await _context.TodoItems.ToListAsync();
+
+            return await _contextDynamic.TodoItems.ToListAsync();
         }
 
         // GET: api/Todo/5

Models/DynamicDbContextFactory.cs

@@ -0,0 +1,33 @@
+using Microsoft.EntityFrameworkCore;
+using System.Data.Entity.Infrastructure;
+using System.Data.Entity;
+using TodoApi.Services;
+
+namespace TodoApi.Models
+{
+
+    public class DynamicDbContextFactory 
+    {
+        private readonly ITenantService _tenantService;
+
+        public DynamicDbContextFactory(ITenantService tenantService)
+        {
+            _tenantService = tenantService;
+        }
+
+
+        public TodoContext CreateDbContext()
+        {
+            var connectionString = _tenantService.GetConnectionString();
+
+            var optionsBuilder = new DbContextOptionsBuilder<TodoContext>();
+
+            //TODO: here need to set the connection string for the database
+            //optionsBuilder.UseSqlServer(connectionString); 
+            //optionsBuilder.UseSqlite(connectionString);
+
+            optionsBuilder.UseInMemoryDatabase(connectionString);
+            return new TodoContext(optionsBuilder.Options);
+        }
+    }
+}

Services/TenantService.cs

@@ -0,0 +1,40 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Configuration;
+using System;
+
+namespace TodoApi.Services
+{
+    public interface ITenantService
+    {
+        string GetConnectionString();
+    }
+    public class TenantService : ITenantService
+    {
+        private readonly IHttpContextAccessor _httpContextAccessor;
+        private readonly IConfiguration _configuration;
+
+        public TenantService(IHttpContextAccessor httpContextAccessor, IConfiguration configuration)
+        {
+            _httpContextAccessor = httpContextAccessor;
+            _configuration = configuration;
+        }
+
+        public string GetConnectionString()
+        {
+            // Extract client ID from header
+            var clientId = _httpContextAccessor.HttpContext?.Request.Headers["X-Client-ID"].ToString();
+
+            if (string.IsNullOrEmpty(clientId))
+                throw new UnauthorizedAccessException("Client ID is missing.");
+
+            // Retrieve the connection string from configuration
+            var connectionString = _configuration.GetSection($"ConnectionStrings:ClientDatabases:{clientId}").Value;
+
+            if (string.IsNullOrEmpty(connectionString))
+                throw new UnauthorizedAccessException("Invalid client ID or connection string not found.");
+
+            return connectionString;
+        }
+
+    }
+}

Startup.cs

@@ -6,6 +6,10 @@
 using Microsoft.EntityFrameworkCore;
 using Microsoft.OpenApi.Models;
 using TodoApi.Models;
+using TodoApi.ContextMiddleware;
+using System.Data.Entity.Infrastructure;
+using System.Data.Entity;
+using TodoApi.Services;
 
 namespace TodoApi
 {
@@ -30,6 +34,11 @@ public void ConfigureServices(IServiceCollection services)
             });
 
             services.AddDbContext<TodoContext>(options => options.UseInMemoryDatabase("TodoList"));
+
+            services.AddHttpContextAccessor();
+            // Add the tenant service
+            services.AddScoped<ITenantService, TenantService>();
+            services.AddScoped<DynamicDbContextFactory>();
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
@@ -50,6 +59,7 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
                 app.UseDeveloperExceptionPage();
             }
 
+           // app.UseMiddleware<ConnectionStringMiddleware>();
             //app.UseHttpsRedirection();
 
             app.UseDefaultFiles();
@@ -60,6 +70,7 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
 
             app.UseAuthorization();
 
+
             app.UseEndpoints(endpoints =>
             {
                 endpoints.MapControllers();

appsettings.Development.json

@@ -5,5 +5,11 @@
       "Microsoft": "Warning",
       "Microsoft.Hosting.Lifetime": "Information"
     }
+  },
+  "ConnectionStrings": {
+    "ClientDatabases": {
+      "ClientA": "DatabaseforClientA",
+      "ClientB": "DatabaseforClientB"
+    }
   }
 }

wwwroot/app/scripts/todoListSvc.js

@@ -4,6 +4,8 @@ angular.module('todoApp')
 
     $http.defaults.useXDomain = true;
     delete $http.defaults.headers.common['X-Requested-With']; 
+    // Add X-Client-ID header to all requests
+    $http.defaults.headers.common['X-Client-ID'] = 'ClientA'; 
 
     return {
         getItems : function(){