Serializing a collection of view models with overridden Equals method

Question

Trying to serialize a collection of a custom type with an overloaded Equals(object obj) method. I am using Newtonsoft.Json.JsonConvert.SerializeObject(object value) to achieve this.

This is my abstract base view model from which the view model in question inherits:

public abstract class BaseCollectibleViewModel
{
    protected abstract bool CompareParameters(object item);

    protected abstract List<int> GetParameters();

    public override bool Equals(object obj)
    {
        if (CompareParameters(obj))
        {
            return true;
        }
        return false;
    }

    public override int GetHashCode()
    {
        int hash = 13;
        foreach (var parameter in GetParameters())
        {
            hash = (hash * 7) + parameter.GetHashCode();
        }

        return hash;
    }

    public static bool operator ==(BaseCollectibleViewModel a, BaseCollectibleViewModel b)
    {
        if (a.Equals(b))
        {
            return true;
        }
        return false;
    }

    public static bool operator !=(BaseCollectibleViewModel a, BaseCollectibleViewModel b)
    {
        if (a.Equals(b))
        {
            return false;
        }
        return true;
    }
}

This is the actual view model:

public class ImagesViewModel : BaseCollectibleViewModel, ISourceImage
{
    public string Name { get; private set; }
    public string Type { get; private set; }
    [ScriptIgnore]
    public Stream Content { get; private set; }
    [ScriptIgnore]
    private HttpPostedFileBase _file;
    [ScriptIgnore]
    public HttpPostedFileBase File
    {
        get
        {
            return _file;
        }
        set
        {
            _file = value;
            Name = File.FileName;
            Type = File.ContentType;
            Content = new MemoryStream();
            File.InputStream.CopyTo(Content);
        }
    }

    protected override bool CompareParameters(object obj)
    {
        var temp = obj as ImagesViewModel;
        if(temp == null)
        {
            return false;
        }
        return
            (Name == temp.Name &&
            Type == temp.Type);
    }

    protected override List<int> GetParameters()
    {
        return new List<int>()
        {
            Name.GetHashCode(),
            Type.GetHashCode()
        };
    }
}

Notice the ScriptIgnore attributes. I even have one on the private field. The program breaks on the == operator of the base class because both of the arguments that get passed are null.

This is the serializing code:

[HttpPost]
public string GetSessionImages()
{
    var imagesInSession = _imagesSessionService.GetCollection();
    return JsonConvert.SerializeObject(imagesInSession, Formatting.Indented);
}

Also this:

The screenshot is showing the implementation of the abstract CompareParameters(object obj) method on the inheriting view model. That stream is the Content property stream, I have checked. Why is this happening?

EDIT: When not overriding Equals I get a JsonSerializationException stating:

{"Error getting value from 'ReadTimeout' on 'System.IO.MemoryStream'."}

EDIT 2: Per dbc's comment I have replaced the attribute [ScriptIgnore] with [JsonIgnore] and the code worked to an extent. However, I had to comment out the operator implementations because the '==' operator would be passed a null value as the BaseCollectibleViewModel b argument.

Answer 1

Since you are using json.net, you must mark members to ignore with [JsonIgnore]:

using Newtonsoft.Json;

public class ImagesViewModel : BaseCollectibleViewModel, ISourceImage
{
    public string Name { get; private set; }
    public string Type { get; private set; }

    [ScriptIgnore]
    [JsonIgnore]
    public Stream Content { get; private set; }

    [ScriptIgnore]
    [JsonIgnore]
    public HttpPostedFileBase File { get { ... } set { ... } }

It is not necessary to mark entirely private members with [JsonIgnore] as these are not serialized by default by Json.NET.

Alternatively, if you do not want your models to have a dependency on Json.NET, you could use conditional property serialization to unconditionally suppress the same members:

public class ImagesViewModel : BaseCollectibleViewModel, ISourceImage
{
    public string Name { get; private set; }
    public string Type { get; private set; }

    [ScriptIgnore]
    public Stream Content { get; private set; }

    public bool ShouldSerializeContent() { return false; }

    [ScriptIgnore]
    public HttpPostedFileBase File { get { ... } set { ... } }

    public bool ShouldSerializeFile() { return false; }

Note that the ShouldSerializeXXX() conditional serialization pattern is also respected by other serializers including XmlSerializer, as explained in ShouldSerialize*() vs *Specified Conditional Serialization Pattern - a side-effect which may be desirable, or not.

(Incidentally, you might want to check that you are not double-serializing your data as shown in JSON.NET Parser *seems* to be double serializing my objects.)