Added collection IsNullOrEmpty extension

Author: jamesmcroft

src/MADE.Collections/CollectionExtensions.cs

@@ -445,5 +445,16 @@ public static void SortDescending<T, TKey>(this ObservableCollection<T> source,
                 idx++;
             }
         }
+
+        /// <summary>Indicates whether the specified collection is <see langword="null" /> or empty (containing no items).</summary>
+        /// <param name="source">The collection to test.</param>
+        /// <typeparam name="T">The type of item in the collection.</typeparam>
+        /// <returns>
+        /// <see langword="true" /> if the <paramref name="source" /> parameter is <see langword="null" /> or empty (containing no items); otherwise, <see langword="false" />.
+        /// </returns>
+        public static bool IsNullOrEmpty<T>(this IEnumerable<T> source)
+        {
+            return source is null || !source.Any();
+        }
     }
 }

tests/MADE.Collections.Tests/Tests/CollectionExtensionsTests.cs

@@ -225,6 +225,69 @@ public void ShouldReturnFalseForInvalidCases(Collection<int> expected, Collectio
             };
         }
 
+        public class WhenValidatingIfCollectionIsNullOrEmpty
+        {
+            [TestCaseSource(nameof(ValidEnumerableCases))]
+            public void ShouldReturnTrueIfEnumerableIsNullOrEmpty(IEnumerable<int> collection)
+            {
+                // Act
+                bool isEmpty = collection.IsNullOrEmpty();
+
+                // Assert
+                isEmpty.ShouldBeTrue();
+            }
+
+            [TestCaseSource(nameof(ValidDictionaryCases))]
+            public void ShouldReturnTrueIfDictionaryIsNullOrEmpty(Dictionary<int, string> collection)
+            {
+                // Act
+                bool isEmpty = collection.IsNullOrEmpty();
+
+                // Assert
+                isEmpty.ShouldBeTrue();
+            }
+
+            [TestCaseSource(nameof(InvalidEnumerableCases))]
+            public void ShouldReturnFalseIfEnumerableIsNotNullOrEmpty(IEnumerable<int> collection)
+            {
+                // Act
+                bool isEmpty = collection.IsNullOrEmpty();
+
+                // Assert
+                isEmpty.ShouldBeFalse();
+            }
+
+            [TestCaseSource(nameof(InvalidDictionaryCases))]
+            public void ShouldReturnFalseIfDictionaryIsNotNullOrEmpty(Dictionary<int, string> collection)
+            {
+                // Act
+                bool isEmpty = collection.IsNullOrEmpty();
+
+                // Assert
+                isEmpty.ShouldBeFalse();
+            }
+
+            private static object[] ValidEnumerableCases =
+            {
+                new object[] {null}, new object[] {new ObservableCollection<int>()},
+            };
+
+            private static object[] ValidDictionaryCases =
+            {
+                new object[] {null}, new object[] {new Dictionary<int, string>()},
+            };
+
+            private static object[] InvalidEnumerableCases =
+            {
+                new object[] {new ObservableCollection<int> {1, 2, 3}},
+            };
+
+            private static object[] InvalidDictionaryCases =
+            {
+                new object[] {new Dictionary<int, string> {{1, "A"}, {2, "B"}, {3, "C"}}},
+            };
+        }
+
         public class WhenSortingObservableCollections
         {
             [Test]
@@ -294,10 +357,8 @@ public void ShouldSortDescendingByComplexType()
                 // Assert
                 collection.ShouldBe(new ComplexObject[]
                 {
-                    new() {Id = 1, Name = "James Croft"},
-                    new() {Id = 3, Name = "Guy Wilmer"},
-                    new() {Id = 0, Name = "Ben Hartley"},
-                    new() {Id = 2, Name = "Adam Llewellyn"},
+                    new() {Id = 1, Name = "James Croft"}, new() {Id = 3, Name = "Guy Wilmer"},
+                    new() {Id = 0, Name = "Ben Hartley"}, new() {Id = 2, Name = "Adam Llewellyn"},
                 });
             }