Perf | memory allocations and performance in SqlBuffer (#2300)

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlBuffer.cs

@@ -96,6 +96,10 @@ internal struct Storage
  internal long _int64; // also used to store Money, UtcDateTime, Date , and Time
  [FieldOffset(0)]
  internal Guid _guid;
+#if NET8_0_OR_GREATER
+ [FieldOffset(0)]
+ internal SqlGuid _sqlGuid;
+#endif
  [FieldOffset(0)]
  internal float _single;
  [FieldOffset(0)]
@@ -109,6 +113,9 @@ internal struct Storage
  private bool _isNull;
  private StorageType _type;
  private Storage _value;
+#if !NET8_0_OR_GREATER
+ private SqlGuid _sqlGuid;
+#endif
  private object _object; // String, SqlBinary, SqlCachedBuffer, SqlString, SqlXml
 
  internal SqlBuffer()
@@ -383,7 +390,11 @@ internal Guid Guid
  }
  else if (StorageType.SqlGuid == _type)
  {
- return _value._guid;
+#if NET8_0_OR_GREATER
+ return _value._sqlGuid.Value;
+#else
+ return _sqlGuid.Value;
+#endif
  }
  return (Guid)Value;
  }
@@ -815,17 +826,26 @@ internal SqlGuid SqlGuid
  }
  else if (StorageType.SqlGuid == _type)
  {
- return IsNull ? SqlGuid.Null : new SqlGuid(_value._guid);
+ if (IsNull)
+ {
+ return SqlGuid.Null;
+ }
+#if NET8_0_OR_GREATER
+ return _value._sqlGuid;
+#else
+ return _sqlGuid;
+#endif
  }
  return (SqlGuid)SqlValue; // anything else we haven't thought of goes through boxing.
  }
  set
  {
  Debug.Assert(IsEmpty, "setting value a second time?");
- if (!value.IsNull)
- {
- _value._guid = value.Value;
- }
+#if NET8_0_OR_GREATER
+ _value._sqlGuid = value;
+#else
+ _sqlGuid = value;
+#endif
  _type = StorageType.SqlGuid;
  _isNull = value.IsNull;
  }