Fixed WeakReferenceKey to use hashcode for comparisons

Author: tippmar-nr

src/Agent/NewRelic/Agent/Extensions/NewRelic.Agent.Extensions/Caching/WeakReferenceKey.cs

@@ -11,35 +11,28 @@ namespace NewRelic.Agent.Extensions.Caching
     /// <typeparam name="T"></typeparam>
     public class WeakReferenceKey<T> where T : class
     {
+        private readonly int _hashCode;
         private WeakReference<T> WeakReference { get; }
 
         public WeakReferenceKey(T cacheKey)
         {
             WeakReference = new WeakReference<T>(cacheKey);
+            _hashCode = cacheKey.GetHashCode(); // store the hashcode since we use it in the Equals method and the object could have been GC'd by the time we need to look for it
         }
 
         public override bool Equals(object obj)
         {
             if (obj is WeakReferenceKey<T> otherKey)
             {
-                if (WeakReference.TryGetTarget(out var thisTarget) &&
-                    otherKey.WeakReference.TryGetTarget(out var otherTarget))
-                {
-                    return ReferenceEquals(thisTarget, otherTarget);
-                }
+                return otherKey.GetHashCode() == _hashCode;
             }
 
             return false;
         }
 
         public override int GetHashCode()
         {
-            if (WeakReference.TryGetTarget(out var target))
-            {
-                return target.GetHashCode();
-            }
-
-            return 0;
+            return _hashCode;
         }
 
         /// <summary>

tests/Agent/UnitTests/NewRelic.Agent.Extensions.Tests/Cache/WeakReferenceKeyTests.cs

@@ -93,24 +93,6 @@ public void GetHashCode_ShouldReturnDifferentHashCodeForDifferentObjects()
             Assert.That(hashCode1, Is.Not.EqualTo(hashCode2));
         }
 
-        [Test]
-        public async Task GetHashCode_ShouldReturnZeroIfTargetIsGarbageCollected()
-        {
-            // Arrange
-            var weakRefKey = GetWeakReferenceKey();
-
-            // Act
-            Assert.That(weakRefKey.Value, Is.Not.Null);
-            // force garbage collection
-            GC.Collect();
-            GC.WaitForPendingFinalizers();
-            await Task.Delay(500);
-            GC.Collect(); // Force another collection
-
-            // Assert
-            Assert.That(weakRefKey.GetHashCode(), Is.EqualTo(0));
-        }
-
         [Test]
         public async Task Value_ShouldReturnNullIfTargetIsGarbageCollected()
         {