Merge pull request #223 from Lombiq/issue/OCC-63

OCC-63: Fix bug in SetItems extension method

Lombiq.HelpfulLibraries.Common/Extensions/CollectionExtensions.cs

@@ -42,6 +42,10 @@ public static void RemoveAll<T>(this ICollection<T> collection, Func<T, bool> pr
     /// </summary>
     public static void SetItems<T>(this ICollection<T> collection, IEnumerable<T> newValues)
     {
+        // If the two variables point to the same object, nothing should be done. Otherwise this would clear the
+        // collection and then add nothing to it.
+        if (Equals(collection, newValues)) return;
+
         collection.Clear();
         collection.AddRange(newValues);
     }

Lombiq.HelpfulLibraries.OrchardCore/Docs/Mvc.md

@@ -5,6 +5,7 @@
 - `OrchardControllerExtensions`: Adds extension methods like `RedirectToContentDisplay(content)` to `Controller` objects.
 - `ResultExecutingContextExtensions`: contains shortcuts for common context operations in `IAsyncResultFilter`s.
 - `ShapeResultExtensions`: Adds extensions methods generating placement strings on your shape description, such as `UseTab()`.
+- `UpdateModelExtensions`: Adds extension methods for working with the `IUpdateModel` such as `GetModelErrors()`.
 - `UrlHelperExtensions`: Adds extension methods to the `@Url` helper, such as `EditContentItemWithTab()`.
 
 ## `TypedRoute`

Lombiq.HelpfulLibraries.OrchardCore/Mvc/UpdateModelExtensions.cs

@@ -0,0 +1,18 @@
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace OrchardCore.DisplayManagement.ModelBinding;
+
+public static class UpdateModelExtensions
+{
+    public static IEnumerable<ModelError> GetModelErrors(this IUpdateModel updateModel) =>
+        updateModel
+            .ModelState
+            .Values
+            .SelectMany(entry => entry.Errors)
+            .Where(error => !string.IsNullOrWhiteSpace(error.ErrorMessage));
+
+    public static IEnumerable<string> GetModelErrorMessages(this IUpdateModel updateModel) =>
+        updateModel.GetModelErrors().Select(error => error.ErrorMessage);
+}