Add tennant validation middleware

Author: deyvidnenchev

NorthwindCRUD/Middlewares/TenantHeaderValidationMiddleware.cs

@@ -0,0 +1,35 @@
+using System.Text.RegularExpressions;
+
+namespace NorthwindCRUD.Middlewares
+{
+    public class TenantHeaderValidationMiddleware
+    {
+        private const string TenantHeaderKey = "X-Tenant-ID";
+
+        private readonly RequestDelegate _next;
+
+        public TenantHeaderValidationMiddleware(RequestDelegate next)
+        {
+            _next = next;
+        }
+
+        public async Task InvokeAsync(HttpContext context)
+        {
+            var tenantHeader = context.Request.Headers[TenantHeaderKey].FirstOrDefault();
+
+            if (tenantHeader != null && !IsTenantValid(tenantHeader))
+            {
+                context.Response.StatusCode = StatusCodes.Status400BadRequest;
+                await context.Response.WriteAsync($"Invalid format for Header {TenantHeaderKey}");
+                return;
+            }
+
+            await _next(context);
+        }
+
+        private bool IsTenantValid(string tenantId)
+        {
+            return Regex.IsMatch(tenantId, "^[A-Za-z0-9-_]{0,40}$");
+        }
+    }
+}

NorthwindCRUD/Program.cs

@@ -11,6 +11,7 @@
 using Newtonsoft.Json.Converters;
 using NorthwindCRUD.Filters;
 using NorthwindCRUD.Helpers;
+using NorthwindCRUD.Middlewares;
 using NorthwindCRUD.Providers;
 using NorthwindCRUD.Services;
 
@@ -132,7 +133,7 @@ public static void Main(string[] args)
 
             // Necessary to detect if it's behind a load balancer, for example changing protocol, port or hostname
             app.UseForwardedHeaders();
-
+            app.UseMiddleware<TenantHeaderValidationMiddleware>();
             app.UseHttpsRedirection();
             app.UseDefaultFiles();
             app.UseStaticFiles();