From d3f8d08a47ce1a65c3f975d9d614f749792e6b88 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 12 Sep 2019 18:39:52 +0200
Subject: [PATCH] Make sure OneTime bindings unsubscribe.

`OneTime` bindings unsubscribe when the first value is pushed, meaning that they unsubscribe _during_ `ExpressionNode.StartListeningCore`. Make sure we handle this by:

- Setting `_listening = true` before calling `StartListeningCore`
- Subscribe to current value in `InpcPropertyAccessorPlugin` before sending current value, because we're unsubscribed when `SendCurrentValue` exits
---
 src/Avalonia.Base/Data/Core/ExpressionNode.cs                   | 2 +-
 .../Data/Core/Plugins/InpcPropertyAccessorPlugin.cs             | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Base/Data/Core/ExpressionNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNode.cs
index ca7d980bcf..c2e5c8e4f3 100644
--- a/src/Avalonia.Base/Data/Core/ExpressionNode.cs
+++ b/src/Avalonia.Base/Data/Core/ExpressionNode.cs
@@ -140,8 +140,8 @@ namespace Avalonia.Data.Core
             }
             else if (target != AvaloniaProperty.UnsetValue)
             {
-                StartListeningCore(_target);
                 _listening = true;
+                StartListeningCore(_target);
             }
             else
             {
diff --git a/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs
index 4716b45340..cbceb58204 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs
@@ -103,8 +103,8 @@ namespace Avalonia.Data.Core.Plugins
 
             protected override void SubscribeCore()
             {
-                SendCurrentValue();
                 SubscribeToChanges();
+                SendCurrentValue();
             }
 
             protected override void UnsubscribeCore()