From dbfa515546ec6c4dd37dd5fd69538a31e0a9fa25 Mon Sep 17 00:00:00 2001
From: "Darrin W. Cullop" <Darrin.Cullop@microsoft.com>
Date: Fri, 10 Apr 2026 00:30:31 -0700
Subject: [PATCH] Refactor SwappableLock to support NET9+ Lock type

Add Lock overloads for SwappableLock.SwapTo and constructor to support
the new System.Threading.Lock type on .NET 9+. Uses #if NET9_0_OR_GREATER
conditional compilation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 src/DynamicData/Internal/SwappableLock.cs | 56 ++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/src/DynamicData/Internal/SwappableLock.cs b/src/DynamicData/Internal/SwappableLock.cs
index 267607e9..5f1f4759 100644
--- a/src/DynamicData/Internal/SwappableLock.cs
+++ b/src/DynamicData/Internal/SwappableLock.cs
@@ -18,23 +18,73 @@ public static SwappableLock CreateAndEnter(object gate)
         return result;
     }
 
+#if NET9_0_OR_GREATER
+    public static SwappableLock CreateAndEnter(Lock gate)
+    {
+        gate.Enter();
+        return new SwappableLock() { _lockGate = gate };
+    }
+#endif
+
     public void SwapTo(object gate)
     {
+#if NET9_0_OR_GREATER
+        if (_gate is null && _lockGate is null)
+            throw new InvalidOperationException("Lock is not initialized");
+#else
         if (_gate is null)
             throw new InvalidOperationException("Lock is not initialized");
+#endif
 
         var hasNewLock = false;
         Monitor.Enter(gate, ref hasNewLock);
 
+#if NET9_0_OR_GREATER
+        if (_lockGate is not null)
+        {
+            _lockGate.Exit();
+            _lockGate = null;
+        }
+        else
+#endif
         if (_hasLock)
-            Monitor.Exit(_gate);
+        {
+            Monitor.Exit(_gate!);
+        }
 
         _hasLock = hasNewLock;
         _gate = gate;
     }
 
+#if NET9_0_OR_GREATER
+    public void SwapTo(Lock gate)
+    {
+        if (_lockGate is null && _gate is null)
+            throw new InvalidOperationException("Lock is not initialized");
+
+        gate.Enter();
+
+        if (_lockGate is not null)
+            _lockGate.Exit();
+        else if (_hasLock)
+            Monitor.Exit(_gate!);
+
+        _lockGate = gate;
+        _hasLock = false;
+        _gate = null;
+    }
+#endif
+
     public void Dispose()
     {
+#if NET9_0_OR_GREATER
+        if (_lockGate is not null)
+        {
+            _lockGate.Exit();
+            _lockGate = null;
+        }
+        else
+#endif
         if (_hasLock && (_gate is not null))
         {
             Monitor.Exit(_gate);
@@ -45,4 +95,8 @@ public void Dispose()
 
     private bool _hasLock;
     private object? _gate;
+
+#if NET9_0_OR_GREATER
+    private Lock? _lockGate;
+#endif
 }