Why is my array serialising into a string

Question

I have created the following test vector class:

public class TestVector
{
   public UInt16 MaxBlockSize { get; }
   public byte[] Payload { get; set; }

   public TestVector(ushort maxBlockSize, byte[] payload)
   {
      MaxBlockSize = maxBlockSize;
       Payload = payload;
   }
 }

In my test, I am populating a list of vectors defined as per:

private static HashSet<TestVector> myVectors = new HashSet<TestVector>();

And then serialising "myVectors" using JsonConvert and write the result to a file as per:

var jsonOuput = JsonConvert.SerializeObject(myVectors , new JsonSerializerSettings{ObjectCreationHandling = ObjectCreationHandling.Replace})

File.WriteAllText(@"e:\MyJson.json", jsonOuput);

Here is a Json typical output (with a list/Hashset composed of 2 vectors):

[
 {
    "MaxBlockSize": 256,
    "Payload": "bjQSAAAAAABvNBIAAAAA..."
  },
  {
    "MaxBlockSize": 256,
    "Payload": "VjQSVzQSWDQS...."
  },
 ]

Now what I do not get is why "Payload" is serialised as a string and not as an array.
My questions are:

1. What is this string format (ASCII code maybe?) and why is it used instead of a byte[] type of representation?
2. Is there a way to get the "Payload" byte[] to be printed in a more readable way?

Answer 1

What is this string format (ASCII code maybe?) and why is it used instead of a byte[] type of representation?

See json.Net documentation for primitive types:

Byte[] String (base 64 encoded)

So the format is base64. This is probably used since it is a reasonably efficient encoding of binary data, encoding 6 bits per character. Encoding values as an array would use much more space.

It is somewhat common to encode images or similar chunks of data as byte arrays. Since these can be large it is useful to keep the size down as much as possible.

Is there a way to get the "Payload" byte[] to be printed in a more readable way?

There are various base64 converters online that can convert it to hex, oct, string, or whatever format you prefer to view your binary data in. But for many applications it is not very useful since the binary data often represents something that is already serialized in some way.