From f8ca3638867ae338510fe06db82f64f4c85e1854 Mon Sep 17 00:00:00 2001
From: Gonzalo Paniagua Javier <gonzalo.mono@gmail.com>
Date: Mon, 20 Jul 2009 02:45:47 +0000
Subject: [PATCH] 2009-07-19 Gonzalo Paniagua Javier <gonzalo@novell.com>

	* Lookup.cs: when there are no matching elements, return an empty
	enumerable. Fixes bug #523386.


svn path=/trunk/mcs/; revision=138190
---
 mcs/class/System.Core/System.Linq/ChangeLog          |  5 +++++
 mcs/class/System.Core/System.Linq/Lookup.cs          |  6 +++++-
 mcs/class/System.Core/Test/System.Linq/LookupTest.cs | 14 ++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/mcs/class/System.Core/System.Linq/ChangeLog b/mcs/class/System.Core/System.Linq/ChangeLog
index 734a0d07a31..8234a3e1da2 100644
--- a/mcs/class/System.Core/System.Linq/ChangeLog
+++ b/mcs/class/System.Core/System.Linq/ChangeLog
@@ -1,3 +1,8 @@
+2009-07-19 Gonzalo Paniagua Javier <gonzalo@novell.com>
+
+	* Lookup.cs: when there are no matching elements, return an empty
+	enumerable. Fixes bug #523386.
+
 2009-05-18  Jb Evain  <jbevain@novell.com>
 
 	* Enumerable.cs (Max, Min): fix generic versions.
diff --git a/mcs/class/System.Core/System.Linq/Lookup.cs b/mcs/class/System.Core/System.Linq/Lookup.cs
index 0398ad6a53a..19affc8433d 100644
--- a/mcs/class/System.Core/System.Linq/Lookup.cs
+++ b/mcs/class/System.Core/System.Linq/Lookup.cs
@@ -44,7 +44,11 @@ namespace System.Linq {
 		}
 
 		public IEnumerable<TElement> this [TKey key] {
-			get { return groups [key]; }
+			get {
+				if (groups.ContainsKey (key))
+					return groups [key];
+				return new TElement [0];
+			}
 		}
 
 		internal Lookup (Dictionary<TKey, List<TElement>> lookup)
diff --git a/mcs/class/System.Core/Test/System.Linq/LookupTest.cs b/mcs/class/System.Core/Test/System.Linq/LookupTest.cs
index 85007758d5f..6f790a5b3c7 100644
--- a/mcs/class/System.Core/Test/System.Linq/LookupTest.cs
+++ b/mcs/class/System.Core/Test/System.Linq/LookupTest.cs
@@ -68,5 +68,19 @@ namespace MonoTests.System.Linq {
 			Assert.AreEqual (0x00ff00, lookup ["GrEeN"].First ());
 			Assert.AreEqual (0x0000ff, lookup ["Blue"].First ());
 		}
+
+		[Test]
+		public void EmptyResult ()
+		{
+			var lookup = GetColors ().ToLookup (
+				c => c.Name,
+				c => c.Value,
+				StringComparer.OrdinalIgnoreCase);
+
+			var l = lookup ["notexist"];
+			Assert.IsNotNull (l);
+			int [] values = (int []) l;
+			Assert.AreEqual (values.Length, 0);
+		}
 	}
 }
-- 
2.11.4.GIT