do a much better job of ripping the inner buffer from MemoryStream

src/StackExchange.Redis/RedisValue.cs

 using System;
 using System.Buffers;
 using System.IO;
+using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Text;
 
@@ -806,7 +807,7 @@ public static RedisValue CreateFrom(MemoryStream stream)
         {
             if (stream == null) return Null;
             if (stream.Length == 0) return Array.Empty<byte>();
-            if(stream.TryGetBuffer(out var segment))
+            if(stream.TryGetBuffer(out var segment) || ReflectionTryGetBuffer(stream, out segment))
             {
                 return new Memory<byte>(segment.Array, segment.Offset, segment.Count);
             }
@@ -817,6 +818,27 @@ public static RedisValue CreateFrom(MemoryStream stream)
             }
         }
 
+        private static readonly FieldInfo
+            s_origin = typeof(MemoryStream).GetField("_origin", BindingFlags.NonPublic | BindingFlags.Instance),
+            s_buffer = typeof(MemoryStream).GetField("_buffer", BindingFlags.NonPublic | BindingFlags.Instance);
+
+        private static bool ReflectionTryGetBuffer(MemoryStream ms, out ArraySegment<byte> buffer)
+        {
+            if (s_origin != null && s_buffer != null)
+            {
+                try
+                {
+                    int offset = (int)s_origin.GetValue(ms);
+                    byte[] arr = (byte[])s_buffer.GetValue(ms);
+                    buffer = new ArraySegment<byte>(arr, offset, checked((int)ms.Length));
+                    return true;
+                }
+                catch { }
+            }
+            buffer = default;
+            return false;
+        }
+
         /// <summary>
         /// Indicates whether the current value has the supplied value as a prefix.
         /// </summary>

tests/StackExchange.Redis.Tests/Values.cs

-using System.Linq;
+using System.IO;
 using System.Text;
 using Xunit;
 using Xunit.Abstractions;
@@ -30,5 +30,22 @@ public void NullValueChecks()
             Assert.False(emptyArr.HasValue);
             Assert.True(emptyArr.IsNullOrEmpty);
         }
+
+        [Fact]
+        public void FromStream()
+        {
+            var arr = Encoding.UTF8.GetBytes("hello world");
+            var ms = new MemoryStream(arr);
+            var val = RedisValue.CreateFrom(ms);
+            Assert.Equal("hello world", (string)val);
+
+            ms = new MemoryStream(arr, 1, 6, false, false);
+            val = RedisValue.CreateFrom(ms);
+            Assert.Equal("ello w", (string)val);
+
+            ms = new MemoryStream(arr, 2, 6, false, true);
+            val = RedisValue.CreateFrom(ms);
+            Assert.Equal("llo wo", (string)val);
+        }
     }
 }