Removing duplicated lines - wip

MainProject/Core/Attributes/ValidateModelStateAutomaticallyAttribute.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace BasicDotnetTemplate.MainProject.Core.Attributes
+{
+    /// <summary>
+    /// Indicates that ModelState validation is handled automatically by an Action Filter.
+    /// Used to suppress SonarCloud warnings about missing ModelState.IsValid checks.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    public class ModelStateValidationHandledByFilterAttribute : Attribute
+    { }
+}

MainProject/Core/Filters/ValidationActionFilter.cs

@@ -0,0 +1,30 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Filters;
+using System.Threading.Tasks;
+
+namespace BasicDotnetTemplate.MainProject.Core.Filters
+{
+    public class ValidationActionFilter : IAsyncActionFilter
+    {
+        private readonly string _requestNotWellFormedMessage = "Request is not well formed";
+
+        public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
+        {
+            if (!context.ModelState.IsValid)
+            {
+                context.Result = new BadRequestObjectResult(new { message = _requestNotWellFormedMessage, errors = context.ModelState });
+                return; 
+            }
+
+            var requestBody = context.ActionArguments.Values.FirstOrDefault(arg => arg != null && !arg.GetType().IsPrimitive && !(arg is string));
+
+            if (requestBody == null)
+            {
+                context.Result = new BadRequestObjectResult(new { message = _requestNotWellFormedMessage });
+                return;
+            }
+
+            await next();
+        }
+    }
+}