Added Collection Extensions, Updated DateTimeExtensions

AMWD.Common/Extensions/CollectionExtensions.cs

@@ -0,0 +1,55 @@
+namespace System.Collections.Generic
+{
+	/// <summary>
+	/// Provides extension methods for generic <see cref="ICollection{T}"/> implementations.
+	/// </summary>
+	public static class CollectionExtensions
+	{
+		/// <summary>
+		/// Add the <paramref name="item"/> to the <paramref name="collection"/> if it is not <see langword="null"/>.
+		/// </summary>
+		/// <typeparam name="T">The type of the elements in the collection</typeparam>
+		/// <param name="collection">The collection.</param>
+		/// <param name="item">The item to add if not <see langword="null"/>.</param>
+		public static void AddIfNotNull<T>(this ICollection<T> collection, T item)
+		{
+#if NET8_0_OR_GREATER
+			ArgumentNullException.ThrowIfNull(collection);
+#else
+			if (collection == null)
+				throw new ArgumentNullException(nameof(collection));
+#endif
+
+			if (item == null)
+				return;
+
+			collection.Add(item);
+		}
+
+		/// <summary>
+		/// Adds a <see cref="AddRange{T}(ICollection{T}, IEnumerable{T})"/> functionallity to <see cref="ICollection{T}"/>.
+		/// </summary>
+		/// <typeparam name="T">The type of the elements in the collection.</typeparam>
+		/// <param name="collection">The collection.</param>
+		/// <param name="items">The items to add.</param>
+		public static void AddRange<T>(this ICollection<T> collection, IEnumerable<T> items)
+		{
+#if NET8_0_OR_GREATER
+			ArgumentNullException.ThrowIfNull(collection);
+			ArgumentNullException.ThrowIfNull(items);
+#else
+			if (collection == null)
+				throw new ArgumentNullException(nameof(collection));
+
+			if (items == null)
+				throw new ArgumentNullException(nameof(items));
+#endif
+
+			if (collection == items)
+				return;
+
+			foreach (var item in items)
+				collection.Add(item);
+		}
+	}
+}