Storing result convert.FromBase64String into postgres bytea

I have a mini system where frontend will pass the file in base64 format to the backend. I used convert.frombase64string in order for me to convert the base64 format into byte array and used file stream to save the file into the server.

The codes are shown as below:

byte[] bytes = Convert.FromBase64String(file.Split(',')[1]);

using (var file = new FileStream("D:test.txt", FileMode.Create))
{
    file.Write(bytes, 0, bytes.Length);
    file.Flush();
}

var db = await _context.insertDB.FromSql("INSERT INTO blobTable (blob) VALUES ('" + bytes + "')").SingleAsync(); 

And this is the result that I select from blobTable.

As the return result from Convert.FromBase64String() is byte array. So that I decided to store this value into my database which is postgres with column bytea[].

The problem is that is it so weird that when I trying to

console.writeline(bytes);

The result is printed as "system.byte[]" instead of the bytes value. So that "system.byte[]" is stored into my database instead of the actual value.

Can anybody tell me how do I store the return value from convert.frombase64string() into postgres bytea[] column? Thanks you.