Add the key in the message on throwing a KeyNotFoundException (#282)

* Add the key in the message on throwing a KeyNotFoundException for trying to access an invalid key in the ResourceDictionary. This helps a lot in tracking down what resource is actually missing. * Fix test build, use C# 6 string interpolation
xamarin · Aug 9, 2016 · 43e90a3 · 43e90a3
1 parent 0a73c0f
commit 43e90a3
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Showing 2 changed files with 11 additions and 2 deletions.
diff --git a/Xamarin.Forms.Core.UnitTests/ResourceDictionaryTests.cs b/Xamarin.Forms.Core.UnitTests/ResourceDictionaryTests.cs
@@ -252,5 +252,14 @@ public void MultiLevelMerge ()
 			elt.Parent = parent;
 			Assert.Fail ();
 		}
-	}
+
+        [Test]
+        public void ShowKeyInExceptionIfNotFound()
+        {
+            var rd = new ResourceDictionary();
+            rd.Add("foo", "bar");
+            var ex = Assert.Throws<KeyNotFoundException>(() => { var foo = rd["test_invalid_key"]; });
+            Assert.That(ex.Message, Is.StringContaining("test_invalid_key"));
+        }
+    }
 }
diff --git a/Xamarin.Forms.Core/ResourceDictionary.cs b/Xamarin.Forms.Core/ResourceDictionary.cs
@@ -98,7 +98,7 @@ public bool ContainsKey(string key)
 					return _innerDictionary[index];
 				if (_mergedInstance != null && _mergedInstance.ContainsKey(index))
 					return _mergedInstance[index];
-				throw new KeyNotFoundException();
+				throw new KeyNotFoundException($"The resource '{index}' is not present in the dictionary.");
 			}
 			set
 			{