que se volvieron locos tratando de encontrar una solución elegante a este problema, ya que parece que todo el mundo por defecto en serializador de Newtonsoft a solucionar este problema. Aunque Newtonsoft proporciona más características, tiene algunos inconvenientes graves. Para enumerar algunos: la necesidad de constructores sin parámetros, comportamiento alocado si desea serializar clases que implementan IEnumerable, y funciona muy mal cuando se usan tipos abstractos (ya que no utiliza el atributo KnownTypes, y la solución alternativa genera un resultado detallado que expone sus espacios de nombres internos a las personas que llaman).
Por otro lado, hay pocos ejemplos sobre cómo personalizar DataContractJsonSerializer cuando se utiliza en una solución MVC4 WebApi.
Me tomó un tiempo encontrar una solución que represente las enumeraciones como cadenas y aborde los problemas conocidos de formato DateTime que viene con el DataContractJsonSerializer.
PARTE I - Ponga estos métodos de extensión en una clase de extensiones ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~
#region JSon
/// <summary>Serializes an object to JSon.</summary>
/// <param name="obj">The object to serialize.</param>
/// <returns>Returns a byte array with the serialized object.</returns>
/// <remarks>This implementation outputs dates in the correct format and enums as string.</remarks>
[SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1650:ElementDocumentationMustBeSpelledCorrectly", Justification = "Reviewed.")]
public static byte[] SerializeJson(this object obj)
{
using (MemoryStream b = new MemoryStream())
{
SerializeJson(obj, b);
return b.ToArray();
}
}
/// <summary>Serializes an object to JSon.</summary>
/// <param name="obj">The object to serialize.</param>
/// <param name="stream">The stream to write to.</param>
/// <remarks>This implementation outputs dates in the correct format and enums as string.</remarks>
[SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1650:ElementDocumentationMustBeSpelledCorrectly", Justification = "Reviewed.")]
public static void SerializeJson(this object obj, Stream stream)
{
var settings = new DataContractJsonSerializerSettings();
settings.DateTimeFormat = new System.Runtime.Serialization.DateTimeFormat("yyyy-MM-dd'T'HH:mm:ssZ");
settings.DataContractSurrogate = new EnumToStringDataContractSurrogate();
var type = obj == null ? typeof(object) : obj.GetType();
var enumerationValue = obj as System.Collections.IEnumerable;
var fixedValue = enumerationValue != null
? type.IsGenericType && !type.GetGenericArguments()[0].IsInterface
? enumerationValue.ToArray(type.GetGenericArguments()[0])
: enumerationValue.OfType<object>().ToArray()
: obj;
if (enumerationValue != null && (!type.IsGenericType || (type.IsGenericType || type.GetGenericArguments()[0].IsInterface)))
{
var firstMember = (fixedValue as System.Collections.IEnumerable).OfType<object>().FirstOrDefault();
if (firstMember != null)
fixedValue = enumerationValue.ToArray(firstMember.GetType());
}
var fixedType = obj == null
? type
: fixedValue.GetType();
var jsonSer = new DataContractJsonSerializer(fixedType, settings);
jsonSer.WriteObject(stream, fixedValue);
}
/// <summary>
/// Deserializes an object.
/// </summary>
/// <typeparam name="T">The output type of the object.</typeparam>
/// <param name="data">The serialized contents.</param>
/// <returns>Returns the typed deserialized object.</returns>
/// <remarks>This implementation outputs dates in the correct format and enums as string.</remarks>
[SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "JSon")]
[SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1650:ElementDocumentationMustBeSpelledCorrectly", Justification = "Reviewed.")]
public static T DeserializeJSon<T>(this byte[] data)
{
using (MemoryStream b = new MemoryStream(data))
return DeserializeJSon<T>(b);
}
/// <summary>Deserializes a JSon object.</summary>
/// <typeparam name="T">The output type of the object.</typeparam>
/// <param name="stream">The stream to read from.</param>
/// <returns>Returns the typed object.</returns>
/// <remarks>This implementation outputs dates in the correct format and enums as string.</remarks>
[SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "JSon")]
[SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1650:ElementDocumentationMustBeSpelledCorrectly", Justification = "Reviewed.")]
public static T DeserializeJSon<T>(this Stream stream)
{
var settings = new DataContractJsonSerializerSettings();
settings.DateTimeFormat = new System.Runtime.Serialization.DateTimeFormat("yyyy-MM-dd'T'HH:mm:ssZ");
settings.DataContractSurrogate = new EnumToStringDataContractSurrogate();
var jsonSer = new DataContractJsonSerializer(typeof(T), settings);
return (T)jsonSer.ReadObject(stream);
}
/// <summary>Deserializes a JSon object.</summary>
/// <param name="data">The serialized contents.</param>
/// <param name="targetType">The target type.</param>
/// <returns>Returns the typed deserialized object.</returns>
/// <remarks>This implementation outputs dates in the correct format and enums as string.</remarks>
[SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "JSon")]
[SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1650:ElementDocumentationMustBeSpelledCorrectly", Justification = "Reviewed.")]
public static object DeserializeJSon(this byte[] data, Type targetType)
{
using (MemoryStream b = new MemoryStream(data))
{
return DeserializeJSon(b, targetType);
}
}
/// <summary>Deserializes a JSon object.</summary>
/// <param name="data">The serialized contents.</param>
/// <param name="targetType">The target type.</param>
/// <returns>Returns the typed deserialized object.</returns>
/// <remarks>This implementation outputs dates in the correct format and enums as string.</remarks>
[SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "JSon")]
[SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1650:ElementDocumentationMustBeSpelledCorrectly", Justification = "Reviewed.")]
public static object DeserializeJSon(this Stream data, Type targetType)
{
var settings = new DataContractJsonSerializerSettings();
settings.DateTimeFormat = new System.Runtime.Serialization.DateTimeFormat("yyyy-MM-dd'T'HH:mm:ssZ");
settings.DataContractSurrogate = new EnumToStringDataContractSurrogate();
var jsonSer = new DataContractJsonSerializer(targetType, settings);
return jsonSer.ReadObject(data);
}
/// <summary>Enumerator contract surrogate.</summary>
internal class EnumToStringDataContractSurrogate : IDataContractSurrogate
{
Type IDataContractSurrogate.GetDataContractType(Type type)
{
return type == typeof(Enum) ? typeof(string) : type;
}
object IDataContractSurrogate.GetDeserializedObject(object obj, Type targetType)
{
if (targetType.IsEnum)
{
return obj == null
? System.Enum.GetValues(targetType).OfType<int>().FirstOrDefault()
: System.Enum.Parse(targetType, obj.ToString());
}
return obj;
}
object IDataContractSurrogate.GetObjectToSerialize(object obj, Type targetType)
{
if (obj is Enum)
{
var pair = Enum.GetName(obj.GetType(), obj);
return pair;
}
return obj;
}
object IDataContractSurrogate.GetCustomDataToExport(Type clrType, Type dataContractType)
{
throw new NotImplementedException();
}
object IDataContractSurrogate.GetCustomDataToExport(System.Reflection.MemberInfo memberInfo, Type dataContractType)
{
throw new NotImplementedException();
}
void IDataContractSurrogate.GetKnownCustomDataTypes(System.Collections.ObjectModel.Collection<Type> customDataTypes)
{
throw new NotImplementedException();
}
Type IDataContractSurrogate.GetReferencedTypeOnImport(string typeName, string typeNamespace, object customData)
{
throw new NotImplementedException();
}
System.CodeDom.CodeTypeDeclaration IDataContractSurrogate.ProcessImportedType(System.CodeDom.CodeTypeDeclaration typeDeclaration, System.CodeDom.CodeCompileUnit compileUnit)
{
throw new NotImplementedException();
}
}
#endregion
/// <summary>Creates an array from a non generic source.</summary>
/// <param name="source">The source.</param>
/// <param name="type">The target type of the array.</param>
/// <returns>Returns a typed array.</returns>
public static Array ToArray(this IEnumerable source, Type type)
{
var param = Expression.Parameter(typeof(IEnumerable), "source");
var cast = Expression.Call(typeof(Enumerable), "Cast", new[] { type }, param);
var toArray = Expression.Call(typeof(Enumerable), "ToArray", new[] { type }, cast);
var lambda = Expression.Lambda<Func<IEnumerable, Array>>(toArray, param).Compile();
return lambda(source);
}
PARTE II - Crear su propio formateador encapsulando el DataContractJsonSerializer ~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/// <summary>Custom implementation of DataContract formatter.</summary>
public class DataContractJsonFormatter : MediaTypeFormatter
{
/// <summary>Creates a new instance.</summary>
public DataContractJsonFormatter()
{
SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("application/json"));
}
/// <summary>Gets if the formatter the write a given type.</summary>
/// <param name="type">The type to handle.</param>
/// <returns>Returns if the formatter the write a given type.</returns>
public override bool CanWriteType(Type type)
{
return true;
}
/// <summary>Gets if the formatter the read a given type.</summary>
/// <param name="type">The type to handle.</param>
/// <returns>Returns if the formatter the read a given type.</returns>
public override bool CanReadType(Type type)
{
return true;
}
/// <summary>Deserializes an object.</summary>
/// <param name="type">The target type.</param>
/// <param name="readStream">The stream to read from.</param>
/// <param name="content">The http content.</param>
/// <param name="formatterLogger">A logger.</param>
/// <returns>Returns the deserialized object.</returns>
public override Task<object> ReadFromStreamAsync(Type type, Stream readStream, System.Net.Http.HttpContent content, IFormatterLogger formatterLogger)
{
var task = Task<object>.Factory.StartNew(() =>
{
return readStream.DeserializeJSon(type);
});
return task;
}
/// <summary>Serializes an object.</summary>
/// <param name="type">The target type.</param>
/// <param name="value">The object to serialize.</param>
/// <param name="writeStream">The stream to write to.</param>
/// <param name="content">The http content.</param>
/// <param name="transportContext">The context.</param>
/// <returns>Returns the deserialized object.</returns>
public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, System.Net.Http.HttpContent content, System.Net.TransportContext transportContext)
{
var task = Task.Factory.StartNew(() =>
{
value.SerializeJson(writeStream);
});
return task;
}
}
PARTE III - Modificar el archivo Global.asax y consumir su nuevo formateador JSON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
/// <summary>Event handlers of when the application starts.</summary>
[SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic")]
protected void Application_Start()
{
//Register my custom DataContract JSon serializer
GlobalConfiguration.Configuration.Formatters.Insert(0, new DataContractJsonFormatter());
//Register areas
AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
// BundleConfig.RegisterBundles(BundleTable.Bundles);
//JSON serialization config
var json = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
json.UseDataContractJsonSerializer = false;
}
Este no es una gran sorpresa, ya que las enum son por defecto de tipo int. – Powerlord
En la serialización de XML, también se recomienda evitar las enumeraciones en los contratos de datos wcf porque crean sutiles problemas compatibles con versiones anteriores. Ver http://stackoverflow.com/questions/326339/do-you-use-enum-types-in-your-wcf-web-services –