Question

really stuck, any help and/or comments would be greatly appreciated!

I’ve written a database program that needs to be able to load contents from a file into a list. So basically i’m trying to use serialization and deserialization for this. The area where the error occurs is in bold and is italicized:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;

namespace ConsoleApplication1
{
    class TheFile
    {
        //Version 1 serialiser, instance specific, so a bit of a pain

        public void SerializeObject(string filename, TheDocument document)
        {
            Stream stream = File.Open(filename, FileMode.Create);
            BinaryFormatter bFormatter = new BinaryFormatter();
            bFormatter.Serialize(stream, document);
            stream.Close();
        }
        public TheDocument DeSerializeObject(string filename)
        {
            TheDocument document;
            Stream stream = File.Open(filename, FileMode.Open);
            BinaryFormatter bFormatter = new BinaryFormatter();
            ***document = (TheDocument)bFormatter.Deserialize(stream);***
            stream.Close();
            return document;
        }
    }
}

The error which i receive is as follows: The input stream is not a valid binary format. The starting contents (in bytes) are: 31-37-2F-30-39-2F-32-30-31-31-20-31-31-3A-30-36-3A …

Answer 1

I have seen this reported somewhere else recently, and I was unable to find an explanation there either. The code as presented looks like it should be fine (although it would benefit greatly from a few using statements, but they won’t break the success case since you are calling .Close()).

However! I would also warn that IMO BinaryFormatter is not a good choice for storage in a database, since that suggests it is desirable to read it back in the future. The fact that BinaryFormatter is type-dependent makes it very very brittle as you version your application. Any of: creating a new app-version, renaming/adding/removing a field, changing a property to an automatically implemented property, changing .NET version, changing platform, … could make your data either unreadable, or readable only by adding a lot of custom binder code.

I strongly suggest that you consider using a contract-based serializer instead of BinaryFormatter; any of: DataContractSerializer (but not NetDataContractSerializer), XmlSerializer, JavascriptSerializer, JSON.Net. If you want binary for size and performance, then protocol buffers (with several C# implementations, including protobuf-net) is designed (by Google) to be version tolerant, small, and fast. Since that list is also cross-platform, it also means your data is safe if, say, you switch platform to Java, Mono, WinRT (the new windows 8 subsystem), PHP, or anything else. BinaryFormatter will not work on any of those.