Remove some unnecessary fixed blocks

src/libraries/Common/src/Interop/Unix/System.Native/Interop.IPAddress.cs

@@ -35,10 +35,7 @@ public bool IsIPv6
             public override unsafe int GetHashCode()
             {
                 HashCode h = default;
-                fixed (byte* ptr = Address)
-                {
-                    h.AddBytes(new ReadOnlySpan<byte>(ptr, IsIPv6 ? IPv6AddressBytes : IPv4AddressBytes));
-                }
+                h.AddBytes(MemoryMarshal.CreateReadOnlySpan(ref Address[0], IsIPv6 ? IPv6AddressBytes : IPv4AddressBytes));
                 return h.ToHashCode();
             }
 
@@ -71,11 +68,8 @@ public bool Equals(IPAddress other)
                     addressByteCount = IPv4AddressBytes;
                 }
 
-                fixed (byte* thisAddress = Address)
-                {
-                    return new ReadOnlySpan<byte>(thisAddress, addressByteCount).SequenceEqual(
-                           new ReadOnlySpan<byte>(other.Address, addressByteCount));
-                }
+                return MemoryMarshal.CreateReadOnlySpan(ref Address[0], addressByteCount).SequenceEqual(
+                       new ReadOnlySpan<byte>(other.Address, addressByteCount));
             }
         }
     }

src/libraries/Common/src/Interop/Windows/Kernel32/Interop.WIN32_FIND_DATA.cs

@@ -22,10 +22,8 @@ internal unsafe struct WIN32_FIND_DATA
             private fixed char _cFileName[MAX_PATH];
             private fixed char _cAlternateFileName[14];
 
-            internal ReadOnlySpan<char> cFileName
-            {
-                get { fixed (char* c = _cFileName) return new ReadOnlySpan<char>(c, MAX_PATH); }
-            }
+            internal ReadOnlySpan<char> cFileName =>
+                MemoryMarshal.CreateReadOnlySpan(ref _cFileName[0], MAX_PATH);
         }
     }
 }

src/libraries/Common/src/Interop/Windows/NtDll/Interop.FILE_FULL_DIR_INFORMATION.cs

@@ -54,7 +54,7 @@ public struct FILE_FULL_DIR_INFORMATION
             public uint EaSize;
 
             private char _fileName;
-            public unsafe ReadOnlySpan<char> FileName { get { fixed (char* c = &_fileName) { return new ReadOnlySpan<char>(c, (int)FileNameLength / sizeof(char)); } } }
+            public unsafe ReadOnlySpan<char> FileName => MemoryMarshal.CreateReadOnlySpan(ref _fileName, (int)FileNameLength / sizeof(char));
 
             /// <summary>
             /// Gets the next info pointer or null if there are no more.

src/libraries/Common/src/Interop/Windows/SChannel/Interop.SecPkgContext_ApplicationProtocol.cs

@@ -29,15 +29,7 @@ internal unsafe struct SecPkgContext_ApplicationProtocol
         public ApplicationProtocolNegotiationExt ProtoNegoExt;
         public byte ProtocolIdSize;
         public fixed byte ProtocolId[MaxProtocolIdSize];
-        public ReadOnlySpan<byte> Protocol
-        {
-            get
-            {
-                fixed (byte* pid = ProtocolId)
-                {
-                    return new ReadOnlySpan<byte>(pid, ProtocolIdSize);
-                }
-            }
-        }
+        public ReadOnlySpan<byte> Protocol =>
+            MemoryMarshal.CreateReadOnlySpan(ref ProtocolId[0], ProtocolIdSize);
     }
 }

src/libraries/Common/src/Interop/Windows/User32/Interop.LOGFONT.cs

@@ -27,10 +27,7 @@ public unsafe struct LOGFONT
             public byte lfQuality;
             public byte lfPitchAndFamily;
             private fixed char _lfFaceName[LF_FACESIZE];
-            public Span<char> lfFaceName
-            {
-                get { fixed (char* c = _lfFaceName) { return new Span<char>(c, LF_FACESIZE); } }
-            }
+            public Span<char> lfFaceName => MemoryMarshal.CreateSpan(ref _lfFaceName[0], LF_FACESIZE);
 
             public override string ToString()
             {

src/libraries/Common/src/Interop/Windows/WinMm/Interop.waveOutGetDevCaps.cs

@@ -50,33 +50,25 @@ public Native(WAVEOUTCAPS managed)
                         wMid = managed.wMid;
                         wPid = managed.wPid;
                         vDriverVersion = managed.vDriverVersion;
-                        fixed (char* pszPname = szPname)
-                        {
-                            managed.szPname.AsSpan().CopyTo(new Span<char>(pszPname, szPnameLength));
-                        }
+                        managed.szPname.CopyTo(MemoryMarshal.CreateSpan(ref szPname[0], szPnameLength));
                         dwFormats = managed.dwFormats;
                         wChannels = managed.wChannels;
                         wReserved1 = managed.wReserved1;
                         dwSupport = managed.dwSupport;
                     }
 
-                    public WAVEOUTCAPS ToManaged()
-                    {
-                        fixed (char* pszPname = szPname)
+                    public WAVEOUTCAPS ToManaged() =>
+                        new WAVEOUTCAPS
                         {
-                            return new WAVEOUTCAPS
-                            {
-                                wMid = wMid,
-                                wPid = wPid,
-                                vDriverVersion = vDriverVersion,
-                                szPname = new Span<char>(pszPname, szPnameLength).ToString(),
-                                dwFormats = dwFormats,
-                                wChannels = wChannels,
-                                wReserved1 = wReserved1,
-                                dwSupport = dwSupport,
-                            };
-                        }
-                    }
+                            wMid = wMid,
+                            wPid = wPid,
+                            vDriverVersion = vDriverVersion,
+                            szPname = MemoryMarshal.CreateReadOnlySpan(ref szPname[0], szPnameLength).ToString(),
+                            dwFormats = dwFormats,
+                            wChannels = wChannels,
+                            wReserved1 = wReserved1,
+                            dwSupport = dwSupport,
+                        };
                 }
             }
 #endif

src/libraries/Common/src/Interop/Windows/WinSock/Interop.WinsockBSD.cs

@@ -89,10 +89,7 @@ public unsafe struct Native
                     public Native(IPv6MulticastRequest managed)
                     {
                         Debug.Assert(managed.MulticastAddress.Length == MulticastAddressLength);
-                        fixed (void* dest = _multicastAddress)
-                        {
-                            managed.MulticastAddress.CopyTo(new Span<byte>(dest, MulticastAddressLength));
-                        }
+                        managed.MulticastAddress.CopyTo(MemoryMarshal.CreateSpan(ref _multicastAddress[0], MulticastAddressLength));
                         _interfaceIndex = managed.InterfaceIndex;
                     }
 
@@ -103,10 +100,7 @@ public IPv6MulticastRequest ToManaged()
                             MulticastAddress = new byte[MulticastAddressLength],
                             InterfaceIndex = _interfaceIndex
                         };
-                        fixed (void* src = _multicastAddress)
-                        {
-                            new Span<byte>(src, 16).CopyTo(managed.MulticastAddress);
-                        }
+                        MemoryMarshal.CreateReadOnlySpan(ref _multicastAddress[0], MulticastAddressLength).CopyTo(managed.MulticastAddress);
                         return managed;
                     }
                 }

src/libraries/Common/src/System/Net/NTAuthentication.Managed.cs

@@ -424,13 +424,10 @@ private static unsafe void SetField(ref MessageField field, int length, int offs
                 throw new Win32Exception(NTE_FAIL);
             }
 
-            fixed (void* ptr = &field)
-            {
-                Span<byte> span = new Span<byte>(ptr, sizeof(MessageField));
-                BinaryPrimitives.WriteInt16LittleEndian(span, (short)length);
-                BinaryPrimitives.WriteInt16LittleEndian(span.Slice(2), (short)length);
-                BinaryPrimitives.WriteInt32LittleEndian(span.Slice(4), offset);
-            }
+            Span<byte> span = MemoryMarshal.AsBytes(MemoryMarshal.CreateSpan(ref field, 1));
+            BinaryPrimitives.WriteInt16LittleEndian(span, (short)length);
+            BinaryPrimitives.WriteInt16LittleEndian(span.Slice(2), (short)length);
+            BinaryPrimitives.WriteInt32LittleEndian(span.Slice(4), offset);
         }
 
         private static void AddToPayload(ref MessageField field, ReadOnlySpan<byte> data, Span<byte> payload, ref int offset)

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIPGlobalProperties.cs

@@ -32,28 +32,12 @@ private unsafe TcpConnectionInformation[] GetTcpConnections(bool listeners)
                     continue;
                 }
 
-                byte[] localBytes = new byte[nativeInfo.LocalEndPoint.NumAddressBytes];
-                fixed (byte* localBytesPtr = localBytes)
-                {
-                    Buffer.MemoryCopy(nativeInfo.LocalEndPoint.AddressBytes, localBytesPtr, localBytes.Length, localBytes.Length);
-                }
-                IPAddress localIPAddress = new IPAddress(localBytes);
+                IPAddress localIPAddress = new IPAddress(new ReadOnlySpan<byte>(nativeInfo.LocalEndPoint.AddressBytes, checked((int)nativeInfo.LocalEndPoint.NumAddressBytes)));
                 IPEndPoint local = new IPEndPoint(localIPAddress, (int)nativeInfo.LocalEndPoint.Port);
 
-                IPAddress remoteIPAddress;
-                if (nativeInfo.RemoteEndPoint.NumAddressBytes == 0)
-                {
-                    remoteIPAddress = IPAddress.Any;
-                }
-                else
-                {
-                    byte[] remoteBytes = new byte[nativeInfo.RemoteEndPoint.NumAddressBytes];
-                    fixed (byte* remoteBytesPtr = &remoteBytes[0])
-                    {
-                        Buffer.MemoryCopy(nativeInfo.RemoteEndPoint.AddressBytes, remoteBytesPtr, remoteBytes.Length, remoteBytes.Length);
-                    }
-                    remoteIPAddress = new IPAddress(remoteBytes);
-                }
+                IPAddress remoteIPAddress = nativeInfo.RemoteEndPoint.NumAddressBytes == 0 ?
+                    IPAddress.Any :
+                    new IPAddress(new ReadOnlySpan<byte>(nativeInfo.RemoteEndPoint.AddressBytes, checked((int)nativeInfo.RemoteEndPoint.NumAddressBytes)));
 
                 IPEndPoint remote = new IPEndPoint(remoteIPAddress, (int)nativeInfo.RemoteEndPoint.Port);
                 connectionInformations[nextResultIndex++] = new SimpleTcpConnectionInformation(local, remote, state);
@@ -101,20 +85,9 @@ public override unsafe IPEndPoint[] GetActiveUdpListeners()
             {
                 Interop.Sys.IPEndPointInfo endPointInfo = infos[i];
                 int port = (int)endPointInfo.Port;
-                IPAddress ipAddress;
-                if (endPointInfo.NumAddressBytes == 0)
-                {
-                    ipAddress = IPAddress.Any;
-                }
-                else
-                {
-                    byte[] bytes = new byte[endPointInfo.NumAddressBytes];
-                    fixed (byte* bytesPtr = &bytes[0])
-                    {
-                        Buffer.MemoryCopy(endPointInfo.AddressBytes, bytesPtr, bytes.Length, bytes.Length);
-                    }
-                    ipAddress = new IPAddress(bytes);
-                }
+                IPAddress ipAddress = endPointInfo.NumAddressBytes == 0 ?
+                    IPAddress.Any :
+                    new IPAddress(new ReadOnlySpan<byte>(endPointInfo.AddressBytes, checked((int)endPointInfo.NumAddressBytes)));
 
                 endPoints[i] = new IPEndPoint(ipAddress, port);
             }

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIpInterfaceProperties.cs

@@ -93,7 +93,7 @@ private static unsafe void OnGatewayFound(void* pContext, Interop.Sys.IpAddressI
         {
             ref Context context = ref Unsafe.As<byte, Context>(ref *(byte*)pContext);
 
-            IPAddress ipAddress = new IPAddress(new Span<byte>(gatewayAddressInfo->AddressBytes, gatewayAddressInfo->NumAddressBytes).ToArray());
+            IPAddress ipAddress = new IPAddress(new ReadOnlySpan<byte>(gatewayAddressInfo->AddressBytes, gatewayAddressInfo->NumAddressBytes));
             if (ipAddress.IsIPv6LinkLocal)
             {
                 // For Link-Local addresses add ScopeId as that is not part of the route entry.

src/libraries/System.Private.CoreLib/src/System/IO/Enumeration/FileSystemEntry.Unix.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
+using System.Runtime.InteropServices;
 
 namespace System.IO.Enumeration
 {
@@ -88,11 +89,8 @@ public ReadOnlySpan<char> FileName
             {
                 if (_directoryEntry.NameLength != 0 && _fileName.Length == 0)
                 {
-                    fixed (char* c = _fileNameBuffer)
-                    {
-                        Span<char> buffer = new Span<char>(c, Interop.Sys.DirectoryEntry.NameBufferSize);
-                        _fileName = _directoryEntry.GetName(buffer);
-                    }
+                    Span<char> buffer = MemoryMarshal.CreateSpan(ref _fileNameBuffer[0], Interop.Sys.DirectoryEntry.NameBufferSize);
+                    _fileName = _directoryEntry.GetName(buffer);
                 }
 
                 return _fileName;

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.Unix.cs

@@ -36,13 +36,7 @@ internal static unsafe int StringToAnsiString(string s, byte* buffer, int buffer
         {
             Debug.Assert(bufferLength >= (s.Length + 1) * SystemMaxDBCSCharSize, "Insufficient buffer length passed to StringToAnsiString");
 
-            int convertedBytes;
-
-            fixed (char* pChar = s)
-            {
-                convertedBytes = Encoding.UTF8.GetBytes(pChar, s.Length, buffer, bufferLength);
-            }
-
+            int convertedBytes = Encoding.UTF8.GetBytes(s, new Span<byte>(buffer, bufferLength));
             buffer[convertedBytes] = 0;
 
             return convertedBytes;

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.cs

@@ -995,14 +995,8 @@ private static unsafe IntPtr StringToHGlobalUTF8(string? s)
 
             IntPtr ptr = AllocHGlobal(checked(nb + 1));
 
-            int nbWritten;
             byte* pbMem = (byte*)ptr;
-
-            fixed (char* firstChar = s)
-            {
-                nbWritten = Encoding.UTF8.GetBytes(firstChar, s.Length, pbMem, nb);
-            }
-
+            int nbWritten = Encoding.UTF8.GetBytes(s, new Span<byte>(pbMem, nb));
             pbMem[nbWritten] = 0;
 
             return ptr;
@@ -1042,14 +1036,8 @@ public static unsafe IntPtr StringToCoTaskMemUTF8(string? s)
 
             IntPtr ptr = AllocCoTaskMem(checked(nb + 1));
 
-            int nbWritten;
             byte* pbMem = (byte*)ptr;
-
-            fixed (char* firstChar = s)
-            {
-                nbWritten = Encoding.UTF8.GetBytes(firstChar, s.Length, pbMem, nb);
-            }
-
+            int nbWritten = Encoding.UTF8.GetBytes(s, new Span<byte>(pbMem, nb));
             pbMem[nbWritten] = 0;
 
             return ptr;