// content.bytes + this.bytes[start, count]
            public override void AppendTo(BinaryContent /*!*/ content, int start, int count)
            {
                if (start > _count - count)
                {
                    throw new ArgumentOutOfRangeException("start");
                }

                content.Append(_data, start, count);
            }
 // content.bytes + this.bytes[start, count]
 public override void AppendTo(BinaryContent/*!*/ content, int start, int count) {
     if (start > _count - count) {
         throw new ArgumentOutOfRangeException("start");
     }
     
     content.Append(_data, start, count);
 }