From 92ebb7f6d8b1485313dbe101d3b3ed8060db87a0 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 12 Aug 2016 19:55:04 +0200
Subject: [PATCH] Log meaningful message for AggregateException.

---
 src/Avalonia.Base/AvaloniaObject.cs           |  2 +-
 .../Utilities/ExceptionUtilities.cs           | 23 +++++++++++++++++++
 .../Xaml/ControlBindingTests.cs               |  3 ++-
 3 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 src/Avalonia.Base/Utilities/ExceptionUtilities.cs

diff --git a/src/Avalonia.Base/AvaloniaObject.cs b/src/Avalonia.Base/AvaloniaObject.cs
index 72f70cab2a..83b0d4e533 100644
--- a/src/Avalonia.Base/AvaloniaObject.cs
+++ b/src/Avalonia.Base/AvaloniaObject.cs
@@ -670,7 +670,7 @@ namespace Avalonia
                         "Error binding to {Target}.{Property}: {Message}",
                         this,
                         property,
-                        notification.Error.Message);
+                        ExceptionUtilities.GetMessage(notification.Error));
                 }
             }
         }
diff --git a/src/Avalonia.Base/Utilities/ExceptionUtilities.cs b/src/Avalonia.Base/Utilities/ExceptionUtilities.cs
new file mode 100644
index 0000000000..fa8c5be788
--- /dev/null
+++ b/src/Avalonia.Base/Utilities/ExceptionUtilities.cs
@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Avalonia.Utilities
+{
+    internal static class ExceptionUtilities
+    {
+        public static string GetMessage(Exception e)
+        {
+            var aggregate = e as AggregateException;
+
+            if (aggregate != null)
+            {
+                return string.Join(" | ", aggregate.InnerExceptions.Select(x => x.Message));
+            }
+
+            return e.Message;
+        }
+    }
+}
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs
index df62a1ed41..029285341b 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs
@@ -43,7 +43,8 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                     pv.Length == 3 &&
                     pv[0] is ProgressBar &&
                     object.ReferenceEquals(pv[1], ProgressBar.ValueProperty) &&
-                    (string)pv[2] == "Could not convert FallbackValue 'bar' to 'System.Double'")
+                    (string)pv[2] == "Object reference not set to an instance of an object. | " + 
+                                     "Could not convert FallbackValue 'bar' to 'System.Double'")
                 {
                     called = true;
                 }