Develop Reference

JSON .NET Custom Name Resolver for Sub-Properties

I have an API that returns a JSON object from a MongoDB in which one of the properties is an "open-ended" document, meaning it can be any valid JSON for that property. I don't know what the names of the properties are ahead of time, they can be any string. I only know that this particular property needs to be serialized exactly how it is stored in the database. So if the property name that was originally stored was "Someproperty", the serialized response in JSON needs to be "Someproperty", NOT "someProperty".
We have this configuration:
ContractResolver = new CamelCasePropertyNamesContractResolver();
in our CustomJsonSerializer, but it is messing with the formatting of the response when returning the "open ended" JSON. It is camel-casing all of these properties when in fact we want the response to be exactly how they are stored in MongoDB (BSON). I know the values are maintaining their case when storing/retrieving via the database, so that is not the issue.
How can I tell JSON.net to essentially bypass the CamelCasePropertyNameResolver for all of the child properties of a particular data point?
EDIT:
Just to give a bit more info, and share what I have already tried:
I thought about overriding the PropertyNameResolver like so:
protected override string ResolvePropertyName(string propertyName)
{
if (propertyName.ToLower().Equals("somedocument"))
{
return propertyName;
}
else return base.ResolvePropertyName(propertyName);
}
However, if I have a JSON structure like this:
{
"Name" : "MyObject",
"DateCreated" : "11/14/2016",
"SomeDocument" :
{
"MyFirstProperty" : "foo",
"mysecondPROPERTY" : "bar",
"another_random_subdoc" :
{
"evenmoredata" : "morestuff"
}
}
}
then I would need all of the properties any child properties' names to remain exactly as is. The above override I posted would (I believe) only ignore on an exact match to "somedocument", and would still camelcase all of the child properties.

What you can do is, for the property in question, create a custom JsonConverter that serializes the property value in question using a different JsonSerializer created with a different contract resolver, like so:
public class AlternateContractResolverConverter : JsonConverter
{
[ThreadStatic]
static Stack<Type> contractResolverTypeStack;
static Stack<Type> ContractResolverTypeStack { get { return contractResolverTypeStack = (contractResolverTypeStack ?? new Stack<Type>()); } }
readonly IContractResolver resolver;
JsonSerializerSettings ExtractAndOverrideSettings(JsonSerializer serializer)
{
var settings = serializer.ExtractSettings();
settings.ContractResolver = resolver;
settings.CheckAdditionalContent = false;
if (settings.PreserveReferencesHandling != PreserveReferencesHandling.None)
{
// Log an error throw an exception?
Debug.WriteLine(string.Format("PreserveReferencesHandling.{0} not supported", serializer.PreserveReferencesHandling));
}
return settings;
}
public AlternateContractResolverConverter(Type resolverType)
{
if (resolverType == null)
throw new ArgumentNullException("resolverType");
resolver = (IContractResolver)Activator.CreateInstance(resolverType);
if (resolver == null)
throw new ArgumentNullException(string.Format("Resolver type {0} not found", resolverType));
}
public override bool CanRead { get { return ContractResolverTypeStack.Count == 0 || ContractResolverTypeStack.Peek() != resolver.GetType(); } }
public override bool CanWrite { get { return ContractResolverTypeStack.Count == 0 || ContractResolverTypeStack.Peek() != resolver.GetType(); } }
public override bool CanConvert(Type objectType)
{
throw new NotImplementedException("This contract resolver is intended to be applied directly with [JsonConverter(typeof(AlternateContractResolverConverter), typeof(SomeContractResolver))] or [JsonProperty(ItemConverterType = typeof(AlternateContractResolverConverter), ItemConverterParameters = ...)]");
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
using (ContractResolverTypeStack.PushUsing(resolver.GetType()))
return JsonSerializer.CreateDefault(ExtractAndOverrideSettings(serializer)).Deserialize(reader, objectType);
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
using (ContractResolverTypeStack.PushUsing(resolver.GetType()))
JsonSerializer.CreateDefault(ExtractAndOverrideSettings(serializer)).Serialize(writer, value);
}
}
internal static class JsonSerializerExtensions
{
public static JsonSerializerSettings ExtractSettings(this JsonSerializer serializer)
{
// There is no built-in API to extract the settings from a JsonSerializer back into JsonSerializerSettings,
// so we have to fake it here.
if (serializer == null)
throw new ArgumentNullException("serializer");
var settings = new JsonSerializerSettings
{
CheckAdditionalContent = serializer.CheckAdditionalContent,
ConstructorHandling = serializer.ConstructorHandling,
ContractResolver = serializer.ContractResolver,
Converters = serializer.Converters,
Context = serializer.Context,
Culture = serializer.Culture,
DateFormatHandling = serializer.DateFormatHandling,
DateFormatString = serializer.DateFormatString,
DateParseHandling = serializer.DateParseHandling,
DateTimeZoneHandling = serializer.DateTimeZoneHandling,
DefaultValueHandling = serializer.DefaultValueHandling,
EqualityComparer = serializer.EqualityComparer,
// No Get access to the error event, so it cannot be copied.
// Error = += serializer.Error
FloatFormatHandling = serializer.FloatFormatHandling,
FloatParseHandling = serializer.FloatParseHandling,
Formatting = serializer.Formatting,
MaxDepth = serializer.MaxDepth,
MetadataPropertyHandling = serializer.MetadataPropertyHandling,
MissingMemberHandling = serializer.MissingMemberHandling,
NullValueHandling = serializer.NullValueHandling,
ObjectCreationHandling = serializer.ObjectCreationHandling,
ReferenceLoopHandling = serializer.ReferenceLoopHandling,
// Copying the reference resolver doesn't work in the default case, since the
// actual BidirectionalDictionary<string, object> mappings are held in the
// JsonSerializerInternalBase.
// See https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/Serialization/DefaultReferenceResolver.cs
ReferenceResolverProvider = () => serializer.ReferenceResolver,
PreserveReferencesHandling = serializer.PreserveReferencesHandling,
StringEscapeHandling = serializer.StringEscapeHandling,
TraceWriter = serializer.TraceWriter,
TypeNameHandling = serializer.TypeNameHandling,
// Changes in Json.NET 10.0.1
//TypeNameAssemblyFormat was obsoleted and replaced with TypeNameAssemblyFormatHandling in Json.NET 10.0.1
//TypeNameAssemblyFormat = serializer.TypeNameAssemblyFormat,
TypeNameAssemblyFormatHandling = serializer.TypeNameAssemblyFormatHandling,
//Binder was obsoleted and replaced with SerializationBinder in Json.NET 10.0.1
//Binder = serializer.Binder,
SerializationBinder = serializer.SerializationBinder,
};
return settings;
}
}
public static class StackExtensions
{
public struct PushValue<T> : IDisposable
{
readonly Stack<T> stack;
public PushValue(T value, Stack<T> stack)
{
this.stack = stack;
stack.Push(value);
}
// By using a disposable struct we avoid the overhead of allocating and freeing an instance of a finalizable class.
public void Dispose()
{
if (stack != null)
stack.Pop();
}
}
public static PushValue<T> PushUsing<T>(this Stack<T> stack, T value)
{
if (stack == null)
throw new ArgumentNullException();
return new PushValue<T>(value, stack);
}
}
Then use it like so:
public class RootObject
{
public string Name { get; set; }
public DateTime DateCreated { get; set; }
[JsonProperty(NamingStrategyType = typeof(DefaultNamingStrategy))]
[JsonConverter(typeof(AlternateContractResolverConverter), typeof(DefaultContractResolver))]
public SomeDocument SomeDocument { get; set; }
}
public class SomeDocument
{
public string MyFirstProperty { get; set; }
public string mysecondPROPERTY { get; set; }
public AnotherRandomSubdoc another_random_subdoc { get; set; }
}
public class AnotherRandomSubdoc
{
public string evenmoredata { get; set; }
public DateTime DateCreated { get; set; }
}
(Here I am assuming you want the "SomeDocument" property name to be serialized verbatim, even though it wasn't entirely clear from your question. To do that, I'm using JsonPropertyAttribute.NamingStrategyType from Json.NET 9.0.1. If you're using an earlier version, you'll need to set the property name explicitly.)
Then the resulting JSON will be:
{
"name": "Question 40597532",
"dateCreated": "2016-11-14T05:00:00Z",
"SomeDocument": {
"MyFirstProperty": "my first property",
"mysecondPROPERTY": "my second property",
"another_random_subdoc": {
"evenmoredata": "even more data",
"DateCreated": "2016-11-14T05:00:00Z"
}
}
}
Note that this solution does NOT work well with preserving object references. If you need them to work together, you may need to consider a stack-based approach similar to the one from Json.NET serialize by depth and attribute
Demo fiddle here.
Incidentally, have you considered storing this JSON as a raw string literal, as in the answer to this question?

I think you should look at this backwards.
Instead of trying to NOT touch the properties you don't know, let that be the default behavior and touch the ones you DO know.
In other words, don't use the CamelCasePropertyNamesContractResolver. Deal with the properties you know appropriately and let the other ones pass through transparently.

Custom JSON Derivative Format

I would like to have a serialization format that is nearly identical to JSON, except that key-values are represented as <key>="<value>" instead of "<key>":"<value>".
With Newtonsoft I made a custom JsonConverter called TsonConverter that works fairly well, except that it can't "see" an embedded dictionary. Given the following type:
public class TraceyData
{
[Safe]
public string Application { get; set; }
[Safe]
public string SessionID { get; set; }
[Safe]
public string TraceID { get; set; }
[Safe]
public string Workflow { get; set; }
[Safe]
public Dictionary<string, string> Tags {get; set; }
[Safe]
public string[] Stuff {get; set;}
}
And the following code:
TsonConverter weird = new TsonConverter();
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.NullValueHandling = NullValueHandling.Ignore;
settings.Converters.Add(weird);
var tracey = new TraceyData();
tracey.TraceID = Guid.NewGuid().ToString();
tracey.SessionID = "5";
tracey.Tags["Referrer"] = "http://www.sky.net/deals";
tracey.Stuff = new string[] { "Alpha", "Bravo", "Charlie" };
tracey.Application = "Responsive";
string stuff = JsonConvert.SerializeObject(tracey, settings);
I get this:
[Application="Responsive" SessionID="5" TraceID="082ef853-92f8-4ce8-9f32-8e4f792fb022" Tags={"Referrer":"http://www.sky.net/deals"} Stuff=["Alpha","Bravo","Charlie"]]
Obviously I have also overridden the StartObject/EndObject notation, replacing { } with [ ]. Otherwise the results are not bad.
However, there is still the problem of the internal dictionary. In order
to convert the dictionary as well to use my <key>="<value>" format, it looks like I must make a deep dictionary converter.
I'm wondering if there is an easier way to do this.
Perhaps the Newtonsoft tool has a "property generator" and "key-value" generator property that I can set that globally handles this for me?
Any suggestions?
And while we're here, I wonder if there is a StartObject/EndObject formatter property override I can set, which would handle the other customization I've shown above. It would be nice to "skip" making JsonConverter tools for these kinds of simple alterations.
Incidentally:
My custom JsonConverter is choosing properties to serialize based on the [Safe] attribute shown in my sample. This is another nice-to-have. It would be wonderful if the JSon settings could expose an "attribute handler" property that lets me override the usual JSon attributes in favor of my own.
I have no need to de-serialize this format. It is intended as a one-way operation. If someone wishes also to explain how to de-serialize my custom format as well that is an interesting bonus, but definitely not necessary to answer this question.
Appendix
Below is the TraceConverter I had made. It references a FieldMetaData class that simply holds property info.
public class TsonConverter : JsonConverter
{
public override bool CanRead
{
get
{
return false;
}
}
public override bool CanConvert(Type ObjectType)
{
return DataClassifier.TestForUserType(ObjectType);
}
public override void WriteJson(
JsonWriter writer, object value, JsonSerializer serializer)
{
Type objType = value.GetType();
var props = objType.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
var propMap = from p in props
from a in p.GetCustomAttributes(typeof(ProfileAttribute), false)
select new FieldMetaData(p, (ProfileAttribute)a);
//writer.WriteStartObject();
writer.WriteStartArray();
bool loopStarted = true;
foreach(var prop in propMap){
object rawValue = prop.GetValue(value);
if (rawValue != null || serializer.NullValueHandling == NullValueHandling.Include)
{
string jsonValue = JsonConvert.SerializeObject(prop.GetValue(value), this);
if (loopStarted)
{
loopStarted = false;
writer.WriteRaw(String.Format("{0}={1}", prop.Name, jsonValue));
}
else
{
writer.WriteRaw(String.Format(" {0}={1}", prop.Name, jsonValue));
}
}
//writer.WriteRaw(String.Format("{0}={1}", prop.Name, prop.GetValue(value)));
//writer.WritePropertyName(prop.Name, false);
//writer.WriteValue(prop.GetValue(value));
}
writer.WriteEndArray();
}
public override object ReadJson(
JsonReader reader, Type objectType,
object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}

Rather than creating your own converter, you're going to need to create your own subclass of JsonWriter that writes to your custom file format. (This is how Json.NET implements its BsonWriter.) In your case, your file format is close enough to JSON that you can inherit from JsonTextWriter:
public class TsonTextWriter : JsonTextWriter
{
TextWriter _writer;
public TsonTextWriter(TextWriter textWriter)
: base(textWriter)
{
if (textWriter == null)
throw new ArgumentNullException("textWriter");
QuoteName = false;
_writer = textWriter;
}
public override void WriteStartObject()
{
SetWriteState(JsonToken.StartObject, null);
_writer.Write('[');
}
protected override void WriteEnd(JsonToken token)
{
switch (token)
{
case JsonToken.EndObject:
_writer.Write(']');
break;
default:
base.WriteEnd(token);
break;
}
}
public override void WritePropertyName(string name)
{
WritePropertyName(name, true);
}
public override void WritePropertyName(string name, bool escape)
{
SetWriteState(JsonToken.PropertyName, name);
var escaped = name;
if (escape)
{
escaped = JsonConvert.ToString(name, '"', StringEscapeHandling);
escaped = escaped.Substring(1, escaped.Length - 2);
}
// Maybe also escape the space character if it appears in a name?
_writer.Write(escaped.Replace("=", #"\u003d"));// Replace "=" with unicode escape sequence.
_writer.Write('=');
}
/// <summary>
/// Writes the JSON value delimiter. (Remove this override if you want to retain the comma separator.)
/// </summary>
protected override void WriteValueDelimiter()
{
_writer.Write(' ');
}
/// <summary>
/// Writes an indent space.
/// </summary>
protected override void WriteIndentSpace()
{
// Do nothing.
}
}
Having done this, now all classes will be serialized to your custom format when you use this writer, for instance:
var tracey = new TraceyData();
tracey.TraceID = Guid.NewGuid().ToString();
tracey.SessionID = "5";
tracey.Tags["Referrer"] = "http://www.sky.net/deals";
tracey.Stuff = new string[] { "Alpha", "Bravo", "Charlie" };
tracey.Application = "Responsive";
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.NullValueHandling = NullValueHandling.Ignore;
using (var sw = new StringWriter())
{
using (var jsonWriter = new TsonTextWriter(sw))
{
JsonSerializer.CreateDefault(settings).Serialize(jsonWriter, tracey);
}
Debug.WriteLine(sw.ToString());
}
Produces the output
[Application="Responsive" SessionID="5" TraceID="2437fe67-9788-47ba-91ce-2e5b670c2a34" Tags=[Referrer="http://www.sky.net/deals"] Stuff=["Alpha" "Bravo" "Charlie"]]
As far as deciding whether to serialize properties based on the presence of a [Safe] attribute, that's sort of a second question. You will need to create your own ContractResolver and override CreateProperty, for instance as shown here: Using JSON.net, how do I prevent serializing properties of a derived class, when used in a base class context?
Update
If you want to retain the comma separator for arrays but not objects, modify WriteValueDelimiter as follows:
/// <summary>
/// Writes the JSON value delimiter. (Remove this override if you want to retain the comma separator.)
/// </summary>
protected override void WriteValueDelimiter()
{
if (WriteState == WriteState.Array)
_writer.Write(',');
else
_writer.Write(' ');
}

JSON.Net deserialization error setting value to property

I want so serialize/deserialize the following model:
public class ReadabilitySettings
{
public ReadabilitySettings() {
}
private bool _reababilityEnabled;
public bool ReadabilityEnabled {
get {
return _reababilityEnabled;
}
set {
_reababilityEnabled = value;
}
}
private string _fontName;
public string FontName {
get {
return _fontName;
}
set {
_fontName = value;
}
}
private bool _isInverted;
public bool IsInverted {
get {
return _isInverted;
}
set {
_isInverted = value;
}
}
public enum FontSizes
{
Small = 0,
Medium = 1,
Large = 2
}
private FontSizes _fontSize;
public FontSizes FontSize { get
{
return _fontSize;
}
set
{
_fontSize = value;
}
}
}
}
I have a list containing instances of the following object:
public class CacheItem<T>
{
public string Key { get; set; }
public T Value { get; set; }
}
I populate the list like so:
list.Add(new CacheItem<ReadabilitySettings>() { Key = "key1", Value = InstanceOfReadabilitySettings };
When I want to serialize this list I call:
var json = JsonConvert.SerializeObject (list);
This works fine. No errors. It gives the following json:
[{"Key":"readbilitySettings","Value":{"ReadabilityEnabled":true,"FontName":"Lora","IsInverted":true,"FontSize":2}}]
When I want to deserialize the list I call:
var list = JsonConvert.DeserializeObject<List<CacheItem<object>>> (json);
This gives me a list of CacheItem's with it's Value property set to a JObject. No errors so far.
When I want the actual instance of ReadabilitySettings I call:
var settings = JsonConvert.DeserializeObject<ReadabilitySettings> (cacheItem.Value.ToString ());
I have to call this since the cacheItem.Value is set to a json string, not to an instance of ReadabilitySettings. The json string is:
{{ "ReadabilityEnabled": true, "FontName": "Lora", "IsInverted": true, "FontSize": 2 }} Newtonsoft.Json.Linq.JObject
Then I get this error: "Error setting value to 'ReadabilityEnabled' on 'Reflect.Mobile.Shared.State.ReadabilitySettings'."
What am I missing? Thanks!
EDIT------
This is the method that throws the error:
public T Get<T> (string key)
{
var items = GetCacheItems (); // this get the initial deserialized list of CacheItems<object> with its value property set to a JObject
if (items == null)
throw new CacheKeyNotFoundException ();
var item = items.Find (q => q.Key == key);
if (item == null)
throw new CacheKeyNotFoundException ();
var result = JsonConvert.DeserializeObject<T> (item.Value.ToString ()); //this throws the error
return result;
}

I've just tried this, which is pretty much copy/pasting your code and it works fine using Newtonsoft.Json v6.0.0.0 (from NuGet):
var list = new List<CacheItem<ReadabilitySettings>>();
list.Add(new CacheItem<ReadabilitySettings>() { Key = "key1", Value = new ReadabilitySettings() { FontName = "FontName", FontSize = ReadabilitySettings.FontSizes.Large, IsInverted = false, ReadabilityEnabled = true } });
var json = JsonConvert.SerializeObject(list);
var list2 = JsonConvert.DeserializeObject<List<CacheItem<object>>>(json);
var settings = JsonConvert.DeserializeObject<ReadabilitySettings>(list2.First().Value.ToString());
However, you don't need the last line. Simply switch List<CacheItem<object>> to List<CacheItem<ReadabilitySettings>> in your call to DeserializeObject and it automatically resolves it:
var list2 = JsonConvert.DeserializeObject<List<CacheItem<ReadabilitySettings>>>(json);
Now list2.First().Value.GetType() = ReadabilitySettings and there's no need to do any further deserialising. Is there a reason you're using object?
Edit:
I'm not sure if this helps you necessarily, but given what you're trying to do have you thought about using a custom converter? I had to do this a few days ago for similar reasons. I had an enum property coming back in my JSON (similar to your key) which gave a hint as to what type a property in my JSON and therefore my deserialised class was. The property in my class was an interface rather than an object but the same principle applies for you.
I used a custom converter to automatically handle creating the object of the correct type cleanly.
Here's a CustomConverter for your scenario. If your key is set to readbilitySettings then result.Value is initialised as ReadabilitySettings.
public class CacheItemConverter : CustomCreationConverter<CacheItem<object>>
{
public override CacheItem<object> Create(Type objectType)
{
return new CacheItem<object>();
}
public CacheItem<object> Create(Type objectType, JObject jObject)
{
var keyProperty = jObject.Property("Key");
if (keyProperty == null)
throw new ArgumentException("Key missing.");
var result = new CacheItem<object>();
var keyValue = keyProperty.First.Value<string>();
if (keyValue.Equals("readbilitySettings", StringComparison.InvariantCultureIgnoreCase))
result.Value = new ReadabilitySettings();
else
throw new ArgumentException(string.Format("Unsupported key {0}", keyValue));
return result;
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
JObject jObject = JObject.Load(reader);
var target = Create(objectType, jObject);
serializer.Populate(jObject.CreateReader(), target);
/* Here your JSON is deserialised and mapped to your object */
return target;
}
}
Usage:
var list = JsonConvert.DeserializeObject<List<CacheItem<object>>>(json, new CacheItemConverter());
Here's a link to a full working example of it:
http://pastebin.com/PJSvFDsT

Managed to solve it. Sample code did not show that ReadabilitySettings also implemented the INotifyPropertyChanged interface. The subsequent eventhandler wired-up to the PropertyChanged event of ReadabilitySettings somewhere else in the project had some errors and thus the deserializer was not able to instantiate ReadabilitySettings :-).
Not a glamorous save but its working... Thanks for your time.

Force binary deserialization to fail when type modified

I'm looking for a non-intrusive way to enforce deserialization to fail under the following circumstances:
The type is not defined in a strongly named assembly.
BinaryFormatter is used.
Since serialized, the type has been modified (e.g. a property has been added).
Below is an illustration/repro of the problem in form of a failing NUnit test. I'm looking for a generic way to make this pass without modifying the Data class, preferably by just setting up the BinaryFormatter during serialization and/or deserialization. I also don't want to involve serialization surrogates, as this is likely to require specific knowledge for each affected type.
Can't find anything in the MSDN docs that helps me though.
[Serializable]
public class Data
{
public string S { get; set; }
}
public class DataSerializationTests
{
/// <summary>
/// This string contains a Base64 encoded serialized instance of the
/// original version of the Data class with no members:
/// [Serializable]
/// public class Data
/// { }
/// </summary>
private const string Base64EncodedEmptyDataVersion =
"AAEAAAD/////AQAAAAAAAAAMAgAAAEtTc2MuU3Rvcm0uRGF0YS5UZXN0cywgV"+
"mVyc2lvbj0xLjAuMC4wLCBDdWx0dXJlPW5ldXRyYWwsIFB1YmxpY0tleVRva2"+
"VuPW51bGwFAQAAABlTc2MuU3Rvcm0uRGF0YS5UZXN0cy5EYXRhAAAAAAIAAAAL";
[Test]
public void Deserialize_FromOriginalEmptyVersionFails()
{
var binaryFormatter = new BinaryFormatter();
var memoryStream = new MemoryStream(Convert.FromBase64String(Base64EncodedEmptyDataVersion));
memoryStream.Seek(0L, SeekOrigin.Begin);
Assert.That(
() => binaryFormatter.Deserialize(memoryStream),
Throws.Exception
);
}
}

I'd recommend a "Java" way here - declare int field in every single serializable class like private int _Serializable = 0; and check that your current version & serialized version match; manually increase when you change properties. If you insist on automated way you'll have to store a lot of metadata and check if current metadata & persisted metadata matches (extra burden on performance/size of serialized data).
Here is the automatic descriptor. Basically you'll have to store TypeDescriptor instance as a part of your binary data & on retrieve check if persisted TypeDescriptor is valid for serialization (IsValidForSerialization) against current TypeDescriptor.
var persistedDescriptor = ...;
var currentDescriptor = Describe(typeof(Foo));
bool isValid = persistedDescriptor.IsValidForSerialization(currentDescriptor);
[Serializable]
[DataContract]
public class TypeDescriptor
{
[DataMember]
public string TypeName { get; set; }
[DataMember]
public IList<FieldDescriptor> Fields { get; set; }
public TypeDescriptor()
{
Fields = new List<FieldDescriptor>();
}
public bool IsValidForSerialization(TypeDescriptor currentType)
{
if (!string.Equals(TypeName, currentType.TypeName, StringComparison.Ordinal))
{
return false;
}
foreach(var field in Fields)
{
var mirrorField = currentType.Fields.FirstOrDefault(f => string.Equals(f.FieldName, field.FieldName, StringComparison.Ordinal));
if (mirrorField == null)
{
return false;
}
if (!field.Type.IsValidForSerialization(mirrorField.Type))
{
return false;
}
}
return true;
}
}
[Serializable]
[DataContract]
public class FieldDescriptor
{
[DataMember]
public TypeDescriptor Type { get; set; }
[DataMember]
public string FieldName { get; set; }
}
private static TypeDescriptor Describe(Type type, IDictionary<Type, TypeDescriptor> knownTypes)
{
if (knownTypes.ContainsKey(type))
{
return knownTypes[type];
}
var descriptor = new TypeDescriptor { TypeName = type.FullName, Fields = new List<FieldDescriptor>() };
knownTypes.Add(type, descriptor);
if (!type.IsPrimitive && type != typeof(string))
{
foreach (var field in type.GetFields(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public).OrderBy(f => f.Name))
{
var attributes = field.GetCustomAttributes(typeof(NonSerializedAttribute), false);
if (attributes != null && attributes.Length > 0)
{
continue;
}
descriptor.Fields.Add(new FieldDescriptor { FieldName = field.Name, Type = Describe(field.FieldType, knownTypes) });
}
}
return descriptor;
}
public static TypeDescriptor Describe(Type type)
{
return Describe(type, new Dictionary<Type, TypeDescriptor>());
}
I also though about some mechanism of shortening size of persisted metadata - like calculating MD5 from xml-serialized or json-serialized TypeDescriptor; but in that case new property/field will mark your object as incompatible for serialization.

C# JSON deserializer does only check format, it doesn't care about object data

I want to deserialize a JSON message received from TCP/IP in my C# application. I have really simple classes with one or two Properties at most, but they are derived. For example:
public class SemiCommand
{
public SemiCommand()
{
UID = string.Empty;
}
public SemiCommand(string uid)
{
UID = uid;
}
public string UID
{
get;
set;
}
public new string ToString()
{
return new JavaScriptSerializer().Serialize(this);
}
}
public class ResponseCommand : SemiCommand
{
protected const string DEFAULT_INFO = "OK";
public ResponseCommand()
{
UID = string.Empty;
Info = DEFAULT_INFO;
}
public ResponseCommand(string uid)
{
UID = uid;
Info = DEFAULT_INFO;
}
public string Response
{
get;
set;
}
public string Info
{
get;
set;
}
public class GetInfoResponseCommand : ResponseCommand
{
public GetInfoResponseCommand()
: base()
{
Response = "GetInfoResponse";
}
public List<ClientProcess> Processes
{
get;
set;
}
}
I made a few attempts with DataMember and DataContract attributes to solve my problem, but it didn't fix it.
The problem lies here:
private Type[] _deserializationTypes = new Type[] { typeof(StartProcessesRequestCommand), typeof(RequestCommand) };
public RequestCommand TranslateTCPMessageToCommand(string messageInString)
{
RequestCommand requestCommand = null;
for (int i = 0; i < _deserializationTypes.Length; i++)
{
try
{
requestCommand = TryDeserialize(_deserializationTypes[i], messageInString);
break;
}
catch
{
}
}
if (requestCommand == null || (requestCommand != null && requestCommand.Command == string.Empty))
{
throw new System.Runtime.Serialization.SerializationException("Unable to deserialize received message");
}
else
{
return requestCommand;
}
}
If i want to deserialize with a proper format, containing all the necessary properties, it works:
This works: {"Response":"SomeResponse","Info":"Information","UID":"123"}
However, this also works: {"nonexistingProperty":"value"}
The second one also creates a RequestCommand with property values set to null.
1st question: How can I force my messagetranslator function to make RequestCommand only if it receives all of the required properties
2nd question: If i have multiple command types which are derived from one or more ancestors, how is it possible, to deserialize it automatically from the "deepest" class if the received properties allow it.
EDIT:
I serialize/deserialize with these two
private RequestCommand TryDeserialize(Type type, string messageInString)
{
JavaScriptSerializer js = new JavaScriptSerializer();
return (RequestCommand)js.Deserialize(messageInString, type);
}
public string TranslateCommandToTCPMessage(ResponseCommand command)
{
JavaScriptSerializer js = new JavaScriptSerializer();
return js.Serialize(command);
}
The break in the try catch supposed to end the loop if the TrySerialize doesn't throw an exception, therefore the deserialization was successful.

If you actually used DataContractJsonSerializer, and you decorated the members / types in question with DataMember / DataContract, you can actually get this to happen. To do this, you can decorate ALL data members with [IsRequired=true]. This would throw an exception if the members weren't present on the wire.
Another option you have is to use IObjectReference, which let you translate one object to another post-serialization, and you can do this depending on what is deserialized from the wire.