c# json.net custom serialization of subobjects - json.net

Question

I am using JSON.NET to serialize a class to JSON. The class contains a property which consists of a list of items, and I want to serialize the items themselves in a custom way (by dynamically including only certain properties, using a customized ContractResolver). So basically I want to serialize the parent class itself in a standard way, with the DefaultContractResolver, but serialize this one property in a custom way, with my own ContractResolver.
JSON.NET has methods that probably allow this but the documentation is rather sketchy. Any help would be appreciated.

Answer 1

I solved this problem with a ContractResolver. The list of objects that I want to serialize is heterogeneous, so I have to pass it two arguments, a list of properties to be serialized, and a list of types to which the property list applies. So it looks like this:
public class DynamicContractResolver : DefaultContractResolver
{
private List<string> mPropertiesToSerialize = null;
private List<string> mItemTypeNames = new List<string>();
public DynamicContractResolver( List<string> propertiesToSerialize,
List<string> itemTypeNames )
{
this.mPropertiesToSerialize = propertiesToSerialize;
this.mItemTypeNames = itemTypeNames;
}
protected override IList<JsonProperty> CreateProperties( Type type, MemberSerialization memberSerialization )
{
IList<JsonProperty> properties = base.CreateProperties( type, memberSerialization );
if( this.mItemTypeNames.Contains( type.Name ) )
properties = properties.Where( p => mPropertiesToSerialize.Contains( p.PropertyName ) ).ToList();
return properties;
}
}
And it is called like this:
DynamicContractResolver contractResolver = new DynamicContractResolver( propsToSerialize, GetItemTypeNames() );
json = JsonConvert.SerializeObject( this, Formatting.None,
new JsonSerializerSettings { ContractResolver = contractResolver } );
where GetItemTypeNames() calls GetType().Name on each of the items in the list that I want to serialize and writes them distinctly to a list.
Sorry my original question was vague and badly phrased, and if somebody has a better solution I am certainly not wedded to this one.

Answer 2

Here's a version that's a bit better. It associates type names with properties, so you can specify which properties you wish to have serialized at every level. The keys to the dictionary are type names; the value is a list of properties to be serialized for each type.
class PropertyContractResolver : DefaultContractResolver
{
public PropertyContractResolver( Dictionary<string, IEnumerable<string>> propsByType )
{
PropertiesByType = propsByType;
}
protected override IList<JsonProperty> CreateProperties( Type type, MemberSerialization memberSerialization )
{
IList<JsonProperty> properties = base.CreateProperties( type, memberSerialization );
if( this.PropertiesByType.ContainsKey( type.Name ) )
{
IEnumerable<string> propsToSerialize = this.PropertiesByType[ type.Name ];
properties = properties.Where( p => propsToSerialize.Contains( p.PropertyName ) ).ToList();
}
return properties;
}
private Dictionary<string, IEnumerable<string>> PropertiesByType
{
get;
set;
}
}