New: Backend changes for new UI

src/Radarr.Http/Validation/EmptyCollectionValidator.cs

@@ -0,0 +1,23 @@
+using System.Collections.Generic;
+using FluentValidation.Validators;
+using NzbDrone.Common.Extensions;
+
+namespace Radarr.Http.Validation
+{
+    public class EmptyCollectionValidator<T> : PropertyValidator
+    {
+        public EmptyCollectionValidator()
+            : base("Collection Must Be Empty")
+        {
+        }
+
+        protected override bool IsValid(PropertyValidatorContext context)
+        {
+            if (context.PropertyValue == null) return true;
+
+            var collection = context.PropertyValue as IEnumerable<T>;
+
+            return collection != null && collection.Empty();
+        }
+    }
+}