Update scope of using.

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Unix.cs

@@ -191,21 +191,19 @@ private void SendFileInternal(string? fileName, ReadOnlySpan<byte> preBuffer, Re
         {
             CheckTransmitFileOptions(flags);
 
-            // Open the file, if any
-            // Open it before we send the preBuffer so that any exception happens first
-            SafeFileHandle? fileHandle = OpenFileHandle(fileName);
-
             SocketError errorCode = SocketError.Success;
 
-            // Send the preBuffer, if any
-            // This will throw on error
-            if (!preBuffer.IsEmpty)
+            // Open the file, if any
+            // Open it before we send the preBuffer so that any exception happens first
+            using (SafeFileHandle? fileHandle = OpenFileHandle(fileName))
             {
-                Send(preBuffer);
-            }
+                // Send the preBuffer, if any
+                // This will throw on error
+                if (!preBuffer.IsEmpty)
+                {
+                    Send(preBuffer);
+                }
 
-            using (fileHandle)
-            {
                 // Send the file, if any
                 if (fileHandle != null)
                 {

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Windows.cs

@@ -397,11 +397,10 @@ private Socket GetOrCreateAcceptSocket(Socket? acceptSocket, bool checkDisconnec
 
         private void SendFileInternal(string? fileName, ReadOnlySpan<byte> preBuffer, ReadOnlySpan<byte> postBuffer, TransmitFileOptions flags)
         {
-            // Open the file, if any
-            SafeFileHandle? fileHandle = OpenFileHandle(fileName);
             SocketError errorCode;
 
-            using (fileHandle)
+            // Open the file, if any
+            using (SafeFileHandle? fileHandle = OpenFileHandle(fileName))
             {
                 // This can throw ObjectDisposedException.
                 errorCode = SocketPal.SendFile(_handle, fileHandle, preBuffer, postBuffer, flags);