How to serialize a DateTimeOffset into a binary stream

Question

I'm wondering what would be the best way to serialize a DateTimeOffset into a binary stream (using a BinaryWriter) and deserialize it again (using a BinaryReader).

To serialize a DateTime, I have:

    public void WriteValue(DateTime value)
    {
        _writer.Write(value.ToBinary());
    }

and

    public DateTime ReadDateTime()
    {
        return DateTime.FromBinary(_reader.ReadInt64());
    }

What is the best approach to serialize/deserialize a DateTimeOffset in terms of performance and storage size?

Answer 1

Based on a comment by Hans Passant, I've came up with the following solution. To serialize:

    public void WriteValue(DateTimeOffset value)
    {
        WriteValue(value.DateTime);
        WriteValue((short)value.Offset.TotalMinutes);
    }

And deserialize:

    public DateTimeOffset ReadDateTimeOffset()
    {
        var dateTime = ReadDateTime();
        var minutes = ReadInt16();
        return new DateTimeOffset(dateTime, TimeSpan.FromMinutes(minutes));
    }

So these method call to the existing serialization methods for DateTime as outlined in the question.

I still wonder if this is the most efficient way to do this. How fast is it to call TotalMinutes and TimeSpan.FromMinutes?

Answer 2

Not that my answer adds much but I have written this little utility for packing and unpacking DateTimeOffset:

public static class DateTimeOffsetExtensions
{
    /// <summary>
    /// Packs DateTimeOffset to bytes
    /// </summary>
    /// <param name="dateTimeOffset"></param>
    /// <returns>10 byte packed bytearray</returns>
    public static byte[] GetBytes(this DateTimeOffset dateTimeOffset)
    {
        return BitConverter.GetBytes(dateTimeOffset.Ticks).
           Concat(BitConverter.GetBytes((Int16)dateTimeOffset.Offset.TotalMinutes)).ToArray();
    }
    /// <summary>
    /// Reads 10 bytes from a buffer and turns back to DateTimeOffset
    /// </summary>
    /// <param name="bytes">Buffer</param>
    /// <param name="offset">Offset to read from</param>
    /// <returns></returns>
    public static DateTimeOffset FromBytes(byte[] bytes, int offset)
    {
        var ticks = BitConverter.ToInt64(bytes, offset);
        var offsetMinutes = BitConverter.ToInt16(bytes, offset + 8);
        return new DateTimeOffset(ticks, TimeSpan.FromMinutes(offsetMinutes));
    }
}