Serialize a private backing data member in .NET 2.0?

Question

I am writing a small xml config file that will be saved and loaded from a specific location (so no using user.config ). My application is .NET 2.0 and can not be moved to a newer version (so no DataContractSerializer ) I am required to implement a "Save Password" option so the password field will be pre-filled in when the user uses the app.

Currently here is how I do it

public class UserSettings
{
    //Snip many other properties...

    public bool SavePassword { get; set; }

    [XmlIgnore]
    public string Password
    {
        get
        {
            string retVal = string.Empty;
            if (ProtectedPassword != null)
            {
                try
                {
                    retVal = Encoding.UTF8.GetString(ProtectedData.Unprotect(ProtectedPassword, _md5.ComputeHash(Encoding.UTF8.GetBytes(this.Username.ToUpper())), DataProtectionScope.LocalMachine));
                }
                catch
                {
                    retVal = string.Empty;
                }
            }
            return retVal;
        }
        set
        {
            ProtectedPassword = ProtectedData.Protect(Encoding.UTF8.GetBytes(value), _md5.ComputeHash(Encoding.UTF8.GetBytes(this.Username.ToUpper())), DataProtectionScope.LocalMachine);
        }
    }

    public byte[] ProtectedPassword;

    private readonly MD5 _md5 = MD5.Create();


    public void Save()
    {
        var xOver = new XmlAttributeOverrides();

        //If Save password is false do not store the encrypted password
        if (this.SavePassword == false)
        {
            var xAttrs = new XmlAttributes();
            xAttrs.XmlIgnore = true;
            xOver.Add(typeof(UserSettings), "ProtectedPassword", xAttrs);
        }

        XmlSerializer xSer = new XmlSerializer(typeof(UserSettings), xOver);
        Directory.CreateDirectory(Path.GetDirectoryName(savePath));
        using(var fs = new FileStream(savePath, FileMode.Create))
        {
            xSer.Serialize(fs, this);
        }

    }

I would like to make ProtectedPassword not public however if I set it to anything other than public xSer.Serialize(fs, this) will not include the property. What do I need to do to make this work correctly?

I know there are many other similar questions to this, however none of them have the .NET 2.0 requirement and use solutions that are not available to a person who is limited to 2.0. Is there any option other than writing a custom XMLSerarlizer or living with the fact that ProtectedPassword is public.

Answer 1

As far as I know, the only way to get this done in .NET 2.0 would be to write a custom implementation of IXmlSerializable .

That said, if the config file does not need to be human readable/editable, I would recommend using the BinaryFormatter to perform a binary serialization, which would capture the private members.