Question

I have this small code that takes an object and convert it to a byte[].
Using C# 4.0.
Can I optimize this further regarding speed then memory usage?
Even small changes would be great – calling this several thousand times+ per second.

    public static byte[] ObjectToByteArray(object obj)
    {
        if (obj == null)
            return null;
        BinaryFormatter bf = new BinaryFormatter();
        MemoryStream ms = new MemoryStream();

        using (ms)
        {
            bf.Serialize(ms, obj);  
        }

        return ms.ToArray();
    }

Answer 1

The problem is that BinaryFormatter is using reflection to read the fields of your objects. Assume you have a simple class with 1 field:

[Serializable]
public class Test
{
    public int A;
}

If you serialize an array of those using BinaryFormatter, it will do something like that for each instance of Test:

int val = (int)typeof(Test).GetField("A").GetValue(obj);
var bytes = BitConverter.GetBytes(val);
stream.Write(bytes, 0, bytes.Length);

The calls to GetField() will consume quite a lot of time.
You can significantly improve the speed using 3 ways:

1. Serialize everything manually. Something similar to this code:

   void SimpleSerialize(Stream stream, Test[] arr)
   {
       foreach (var obj in arr)
       {
           var bytes = BitConverter.GetBytes(obj.A);
           stream.Write(bytes, 0, bytes.Length);
       }
   }
   

2. Generate a custom serialization class on-the-fly using Reflection.Emit functionality. This is more generic and “clean”, but requires a lot of effort.

3. If you’re fine with it, use some third-party serializer that suits your needs.