Remove dead code from ResourceUpdater (dotnet#120132)

After dotnet#120029, some of the code was unreachable. This
change removes that code and standardizes the field style to the .NET Code Style guidelines.

Author: agocke

src/installer/managed/Microsoft.NET.HostModel/ResourceUpdater.cs

@@ -15,10 +15,10 @@ namespace Microsoft.NET.HostModel
     /// </summary>
     public sealed class ResourceUpdater : IDisposable
     {
-        private readonly FileStream stream;
+        private readonly FileStream _stream;
         private readonly PEReader _reader;
         private ResourceData _resourceData;
-        private readonly bool leaveOpen;
+        private readonly bool _leaveOpen;
 
         /// <summary>
         /// Create a resource updater for the given PE file.
@@ -39,18 +39,24 @@ public ResourceUpdater(string peFile)
         /// </summary>
         public ResourceUpdater(FileStream stream, bool leaveOpen = false)
         {
-            this.stream = stream;
-            this.leaveOpen = leaveOpen;
+#if NET
+            ArgumentNullException.ThrowIfNull(stream);
+#endif
+
+            _stream = stream;
+            _leaveOpen = leaveOpen;
             try
             {
-                this.stream.Seek(0, SeekOrigin.Begin);
-                _reader = new PEReader(this.stream, PEStreamOptions.LeaveOpen);
+                _stream.Seek(0, SeekOrigin.Begin);
+                _reader = new PEReader(_stream, PEStreamOptions.LeaveOpen);
                 _resourceData = new ResourceData(_reader);
             }
             catch (Exception)
             {
                 if (!leaveOpen)
-                    this.stream?.Dispose();
+                {
+                    _stream.Dispose();
+                }
                 throw;
             }
         }
@@ -185,12 +191,12 @@ public void Update()
 
             int trailingSectionVirtualStart = rsrcVirtualAddress + rsrcOriginalVirtualSize;
             int trailingSectionStart = rsrcPointerToRawData + rsrcOriginalRawDataSize;
-            int trailingSectionLength = (int)(stream.Length - trailingSectionStart);
+            int trailingSectionLength = (int)(_stream.Length - trailingSectionStart);
 
             bool needsMoveTrailingSections = !isRsrcIsLastSection && delta > 0;
             long finalImageSize = trailingSectionStart + Math.Max(delta, 0) + trailingSectionLength;
 
-            using (var mmap = MemoryMappedFile.CreateFromFile(stream, null, finalImageSize, MemoryMappedFileAccess.ReadWrite, HandleInheritability.None, true))
+            using (var mmap = MemoryMappedFile.CreateFromFile(_stream, null, finalImageSize, MemoryMappedFileAccess.ReadWrite, HandleInheritability.None, true))
             using (MemoryMappedViewAccessor accessor = mmap.CreateViewAccessor(0, finalImageSize, MemoryMappedFileAccess.ReadWrite))
             {
                 int peSignatureOffset = ReadI32(accessor, PEOffsets.DosStub.PESignatureOffset);
@@ -327,19 +333,10 @@ private static void ThrowExceptionForInvalidUpdate()
 
         public void Dispose()
         {
-            Dispose(true);
-            GC.SuppressFinalize(this);
-        }
-
-        private void Dispose(bool disposing)
-        {
-            if (disposing)
+            _reader.Dispose();
+            if (!_leaveOpen)
             {
-                _reader.Dispose();
-                if (!leaveOpen)
-                {
-                    stream.Dispose();
-                }
+                _stream.Dispose();
             }
         }
     }