1 files changed, 6 insertions, 17 deletions
diff --git a/src/MessagePack/StringEncoding.cs b/src/MessagePack/StringEncoding.cs
index 318ce955..f7ba9ecf 100644
--- a/src/MessagePack/StringEncoding.cs
+++ b/src/MessagePack/StringEncoding.cs
@@ -1,4 +1,7 @@
-using System;
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using System.Text;
 
 namespace MessagePack
@@ -7,20 +10,7 @@ namespace MessagePack
     {
         internal static readonly Encoding UTF8 = new UTF8Encoding(false);
 
-        internal static unsafe int GetBytes(this Encoding encoding, ReadOnlySpan<char> chars, Span<byte> bytes)
-        {
-            if (chars.Length == 0)
-            {
-                return 0;
-            }
-
-            fixed (char* pChars = &chars[0])
-            fixed (byte* pBytes = &bytes[0])
-            {
-                return encoding.GetBytes(pChars, chars.Length, pBytes, bytes.Length);
-            }
-        }
-
+#if !NETCOREAPP2_1 // Define the extension method only where an instance method does not already exist.
         internal static unsafe string GetString(this Encoding encoding, ReadOnlySpan<byte> bytes)
         {
             if (bytes.Length == 0)
@@ -33,7 +23,6 @@ namespace MessagePack
                 return encoding.GetString(pBytes, bytes.Length);
             }
         }
-
-        internal static unsafe int GetBytes(this Encoding encoding, string chars, Span<byte> bytes) => GetBytes(encoding, chars.AsSpan(), bytes);
+#endif
     }
 }