Added extension method: AbpCollectionExtensions.AddIfNotContains

src/Volo.Abp.Core/System/Collections/Generic/AbpCollectionExtensions.cs

@@ -20,7 +20,7 @@ namespace System.Collections.Generic
         /// <summary>
         /// Adds an item to the collection if it's not already in the collection.
         /// </summary>
-        /// <param name="source">Collection</param>
+        /// <param name="source">The collection</param>
         /// <param name="item">Item to check and add</param>
         /// <typeparam name="T">Type of the items in the collection</typeparam>
         /// <returns>Returns True if added, returns False if not.</returns>
@@ -38,7 +38,30 @@ namespace System.Collections.Generic
         }
 
         /// <summary>
-        /// Removed all items from a collection those satisfy the given <paramref name="predicate"/>.
+        /// Adds an item to the collection if it's not already in the collection based on the given <paramref name="predicate"/>.
+        /// </summary>
+        /// <param name="source">The collection</param>
+        /// <param name="predicate">The condition to decide if the item is already in the collection</param>
+        /// <param name="itemFactory">A factory that returns the item</param>
+        /// <typeparam name="T">Type of the items in the collection</typeparam>
+        /// <returns>Returns True if added, returns False if not.</returns>
+        public static bool AddIfNotContains<T>([NotNull] this ICollection<T> source, [NotNull] Func<T, bool> predicate, [NotNull] Func<T> itemFactory)
+        {
+            Check.NotNull(source, nameof(source));
+            Check.NotNull(source, nameof(predicate));
+            Check.NotNull(itemFactory, nameof(itemFactory));
+
+            if (source.Any(predicate))
+            {
+                return false;
+            }
+
+            source.Add(itemFactory());
+            return true;
+        }
+
+        /// <summary>
+        /// Removed all items from the collection those satisfy the given <paramref name="predicate"/>.
         /// </summary>
         /// <typeparam name="T">Type of the items in the collection</typeparam>
         /// <param name="source">The collection</param>

test/Volo.Abp.Core.Tests/System/Collections/Generic/AbpCollectionExtensions_Tests.cs

@@ -0,0 +1,26 @@
+using Shouldly;
+using Xunit;
+
+namespace System.Collections.Generic
+{
+    public class AbpCollectionExtensions_Tests
+    {
+        [Fact]
+        public void AddIfNotContains_With_Predicate()
+        {
+            var collection = new List<int> {4, 5, 6};
+
+            collection.AddIfNotContains(x => x == 5, () => 5);
+            collection.Count.ShouldBe(3);
+
+            collection.AddIfNotContains(x => x == 42, () => 42);
+            collection.Count.ShouldBe(4);
+
+            collection.AddIfNotContains(x => x < 8, () => 8);
+            collection.Count.ShouldBe(4);
+
+            collection.AddIfNotContains(x => x > 999, () => 8);
+            collection.Count.ShouldBe(5);
+        }
+    }
+}