From c48cb5227921d9bb9a70c21c4344cd1b4ab2e90d Mon Sep 17 00:00:00 2001
From: Bradley Grainger <bgrainger@gmail.com>
Date: Sun, 7 Feb 2010 01:27:12 -0800
Subject: [PATCH] Added EmptyIfNull. Closes #9.

From http://code.logos.com/blog/2008/03/emptyifnull.html
---
 src/Logos.Utility/EnumerableUtility.cs              | 11 +++++++++++
 tests/Logos.Utility.Tests/EnumerableUtilityTests.cs | 12 ++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/src/Logos.Utility/EnumerableUtility.cs b/src/Logos.Utility/EnumerableUtility.cs
index 543503d..6a2bc36 100644
--- a/src/Logos.Utility/EnumerableUtility.cs
+++ b/src/Logos.Utility/EnumerableUtility.cs
@@ -10,6 +10,17 @@ namespace Logos.Utility
 	/// </summary>
 	public static class EnumerableUtility
 	{
+		/// <summary>
+		/// Returns the source sequence, or an empty sequence if <paramref name="source"/> is <c>null</c>.
+		/// </summary>
+		/// <param name="source">The source sequence.</param>
+		/// <returns>The source sequence, or an empty sequence if <paramref name="source"/> is <c>null</c>.</returns>
+		/// <remarks>See <a href="http://code.logos.com/blog/2008/03/emptyifnull.html">EmptyIfNull</a>.</remarks>
+		public static IEnumerable<T> EmptyIfNull<T>(this IEnumerable<T> source)
+		{
+			return source ?? Enumerable.Empty<T>();
+		}
+
 		/// <summary>
 		/// Computes the sum of a sequence of <see cref="Nullable{Decimal}"/> values.
 		/// </summary>
diff --git a/tests/Logos.Utility.Tests/EnumerableUtilityTests.cs b/tests/Logos.Utility.Tests/EnumerableUtilityTests.cs
index 4e523da..468021f 100644
--- a/tests/Logos.Utility.Tests/EnumerableUtilityTests.cs
+++ b/tests/Logos.Utility.Tests/EnumerableUtilityTests.cs
@@ -9,6 +9,18 @@ namespace Logos.Utility.Tests
 	[TestFixture]
 	public class EnumerableUtilityTests
 	{
+		[Test]
+		public void EmptyIfNullNull()
+		{
+			CollectionAssert.AreEqual(new int[0], ((IEnumerable<int>) null).EmptyIfNull());
+		}
+
+		[Test]
+		public void EmptyIfNullNonNull()
+		{
+			CollectionAssert.AreEqual(new[] { 1, 2 }, (new[] { 1, 2 }).EmptyIfNull());
+		}
+
 		const int NullInt = 1234567;
 
 		[TestCase(new[] { 1, 2, 3, 4, 5 }, 15)]