From 5eeccf0c10515e39b1e786df15719b4dbc946ca1 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 15 Oct 2015 23:03:10 +0200
Subject: [PATCH] Special case string -> bool conversion.

---
 .../Perspex.Markup/Binding/LogicalNotNode.cs  | 24 +++++++++++++++----
 .../ExpressionObserverTests_Negation.cs       |  2 +-
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/Markup/Perspex.Markup/Binding/LogicalNotNode.cs b/src/Markup/Perspex.Markup/Binding/LogicalNotNode.cs
index 81ce06c301..4e36336db1 100644
--- a/src/Markup/Perspex.Markup/Binding/LogicalNotNode.cs
+++ b/src/Markup/Perspex.Markup/Binding/LogicalNotNode.cs
@@ -23,14 +23,28 @@ namespace Perspex.Markup.Binding
         {
             if (v != PerspexProperty.UnsetValue)
             {
-                try
+                var s = v as string;
+
+                if (s != null)
                 {
-                    var boolean = Convert.ToBoolean(v, CultureInfo.InvariantCulture);
-                    return !boolean;
+                    bool result;
+
+                    if (bool.TryParse(s, out result))
+                    {
+                        return !result;
+                    }
                 }
-                catch
+                else
                 {
-                    // TODO: Maybe should log something here.
+                    try
+                    {
+                        var boolean = Convert.ToBoolean(v, CultureInfo.InvariantCulture);
+                        return !boolean;
+                    }
+                    catch
+                    {
+                        // TODO: Maybe should log something here.
+                    }
                 }
             }
 
diff --git a/tests/Perspex.Markup.UnitTests/Binding/ExpressionObserverTests_Negation.cs b/tests/Perspex.Markup.UnitTests/Binding/ExpressionObserverTests_Negation.cs
index 2019b884b0..9164002b18 100644
--- a/tests/Perspex.Markup.UnitTests/Binding/ExpressionObserverTests_Negation.cs
+++ b/tests/Perspex.Markup.UnitTests/Binding/ExpressionObserverTests_Negation.cs
@@ -61,7 +61,7 @@ namespace Perspex.Markup.UnitTests.Binding
         }
 
         [Fact]
-        public async void Should_Return_Empty_For_String_Not_Convertible_To_Boolean()
+        public async void Should_Return_UnsetValue_For_String_Not_Convertible_To_Boolean()
         {
             var data = new { Foo = "foo" };
             var target = new ExpressionObserver(data, "!Foo");