From db3adaa104ec69502c53cdf72f83568a7478c822 Mon Sep 17 00:00:00 2001
From: John Cummings <john.cummings@quantitech.com>
Date: Thu, 23 Jul 2020 11:59:42 -0500
Subject: [PATCH 1/2] fix: avoid throwing ArgumentNullException from OAPH.Value
 (#2455)

Ensure OAPH CompositeDisposable is not null before subscribing
Add unit test to cover case where OAPH has been disposed
---
 .../ObservableAsPropertyHelperTest.cs         | 19 +++++++++++++++++++
 .../ObservableAsPropertyHelper.cs             |  7 ++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs b/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs
index 205aa59951..d5074c94d7 100644
--- a/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs
+++ b/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs
@@ -162,6 +162,25 @@ public void OAPHDeferSubscriptionParameterIsSubscribedIsNotTrueInitially()
             Assert.True(fixture.IsSubscribed);
         }
 
+        [Fact]
+        public void OAPHDeferSubscriptionShouldNotThrowIfDisposed()
+        {
+            var observable = Observable.Create<int>(o =>
+            {
+                o.OnNext(42);
+                o.OnCompleted();
+
+                return Disposable.Empty;
+            });
+
+            var fixture = new ObservableAsPropertyHelper<int>(observable, _ => { }, 0, true);
+
+            Assert.False(fixture.IsSubscribed);
+            fixture.Dispose();
+            var ex = Record.Exception(() => Assert.Equal(0, fixture.Value));
+            Assert.Null(ex);
+        }
+
         [Fact]
         public void OAPHShouldRethrowErrors()
         {
diff --git a/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs b/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs
index 277dadb3cd..d426d9f0f0 100644
--- a/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs
+++ b/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs
@@ -136,7 +136,12 @@ public T Value
             {
                 if (Interlocked.CompareExchange(ref _activated, 1, 0) == 0)
                 {
-                    _source.Subscribe(_subject).DisposeWith(_disposable);
+                    // Do not subscribe if disposed
+                    var localReferenceInCaseDisposeIsCalled = _disposable;
+                    if (localReferenceInCaseDisposeIsCalled != null)
+                    {
+                        _source.Subscribe(_subject).DisposeWith(localReferenceInCaseDisposeIsCalled);
+                    }
                 }
 
                 return _lastValue;

From e2bffe9a89d3f79157e3e8405a0d3b2e8597b9fe Mon Sep 17 00:00:00 2001
From: John Cummings <john.cummings@quantitech.com>
Date: Thu, 23 Jul 2020 12:08:03 -0500
Subject: [PATCH 2/2] docs: remove duplicate words in OAPH documentation

---
 .../ObservableForProperty/ObservableAsPropertyHelper.cs       | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs b/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs
index d426d9f0f0..cbf0c4515b 100644
--- a/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs
+++ b/src/ReactiveUI/ObservableForProperty/ObservableAsPropertyHelper.cs
@@ -48,7 +48,7 @@ public sealed class ObservableAsPropertyHelper<T> : IHandleObservableErrors, IDi
         /// A value indicating whether the <see cref="ObservableAsPropertyHelper{T}"/>
         /// should defer the subscription to the <paramref name="observable"/> source
         /// until the first call to <see cref="Value"/>, or if it should immediately
-        /// subscribe to the the <paramref name="observable"/> source.
+        /// subscribe to the <paramref name="observable"/> source.
         /// </param>
         /// <param name="scheduler">
         /// The scheduler that the notifications will be provided on -
@@ -85,7 +85,7 @@ public ObservableAsPropertyHelper(
         /// A value indicating whether the <see cref="ObservableAsPropertyHelper{T}"/>
         /// should defer the subscription to the <paramref name="observable"/> source
         /// until the first call to <see cref="Value"/>, or if it should immediately
-        /// subscribe to the the <paramref name="observable"/> source.
+        /// subscribe to the <paramref name="observable"/> source.
         /// </param>
         /// <param name="scheduler">
         /// The scheduler that the notifications will provided on - this