Expanding Rentering.com's answer, in scenarios where a whole graph of many types is to be taken care of, and you're looking for a strongly typed solution, this class can help, see usage (fluent) below. It operates as either a black-list or white-list per type. A type cannot be both (Gist - also contains global ignore list).
public class PropertyFilterResolver : DefaultContractResolver
{
const string _Err = "A type can be either in the include list or the ignore list.";
Dictionary<Type, IEnumerable<string>> _IgnorePropertiesMap = new Dictionary<Type, IEnumerable<string>>();
Dictionary<Type, IEnumerable<string>> _IncludePropertiesMap = new Dictionary<Type, IEnumerable<string>>();
public PropertyFilterResolver SetIgnoredProperties<T>(params Expression<Func<T, object>>[] propertyAccessors)
{
if (propertyAccessors == null) return this;
if (_IncludePropertiesMap.ContainsKey(typeof(T))) throw new ArgumentException(_Err);
var properties = propertyAccessors.Select(GetPropertyName);
_IgnorePropertiesMap[typeof(T)] = properties.ToArray();
return this;
}
public PropertyFilterResolver SetIncludedProperties<T>(params Expression<Func<T, object>>[] propertyAccessors)
{
if (propertyAccessors == null)
return this;
if (_IgnorePropertiesMap.ContainsKey(typeof(T))) throw new ArgumentException(_Err);
var properties = propertyAccessors.Select(GetPropertyName);
_IncludePropertiesMap[typeof(T)] = properties.ToArray();
return this;
}
protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
{
var properties = base.CreateProperties(type, memberSerialization);
var isIgnoreList = _IgnorePropertiesMap.TryGetValue(type, out IEnumerable<string> map);
if (!isIgnoreList && !_IncludePropertiesMap.TryGetValue(type, out map))
return properties;
Func<JsonProperty, bool> predicate = jp => map.Contains(jp.PropertyName) == !isIgnoreList;
return properties.Where(predicate).ToArray();
}
string GetPropertyName<TSource, TProperty>(
Expression<Func<TSource, TProperty>> propertyLambda)
{
if (!(propertyLambda.Body is MemberExpression member))
throw new ArgumentException($"Expression '{propertyLambda}' refers to a method, not a property.");
if (!(member.Member is PropertyInfo propInfo))
throw new ArgumentException($"Expression '{propertyLambda}' refers to a field, not a property.");
var type = typeof(TSource);
if (!type.GetTypeInfo().IsAssignableFrom(propInfo.DeclaringType.GetTypeInfo()))
throw new ArgumentException($"Expresion '{propertyLambda}' refers to a property that is not from type '{type}'.");
return propInfo.Name;
}
}
Usage:
var resolver = new PropertyFilterResolver()
.SetIncludedProperties<User>(
u => u.Id,
u => u.UnitId)
.SetIgnoredProperties<Person>(
r => r.Responders)
.SetIncludedProperties<Blog>(
b => b.Id)
.Ignore(nameof(IChangeTracking.IsChanged)); //see gist