Develop Reference

C# reflection get all property information inside the proerperties with custom attribute

I am writing a method for extracting all properties from an object (including properties of its own) with custom attribute . For example
public class SomeModel
{
[Custom]
public string Name { get; set; }
public string TestData { get; set; }
[Custom]
public string Surname { get; set; }
public InnerModel InnerModel { get; set; }
}
And Inner Model :
public class InnerModel
{
public string Id { get; set; } = "TestID";
[Custom]
public string Year { get; set; }
public ThirdObject HidedObject { get; set; }
}
And the third one :
public class ThirdObject
{
[Custom]
public string HidedName { get; set; }
}
I need to find all properties with "Custom" attribute .
Testing :
SomeModel model = new SomeModel()
{
Name = "farid",
Surname = "Ismayilzada",
TestData = "Test" ,
InnerModel = new InnerModel() { Year ="2022" , HidedObject= New ThirdObject{ HidedName="Secret"}}
};
I need to write the method
GetMyProperties(model) => List<PropInf>()
[PropertyName= Name,Value=Farid ,Route="Name" ]
[PropertyName= Surname,Value=Ismayilzada,Route="Surname" ]
[PropertyName= Year,Value=2022,Route="InnerModel.Year" ]
[PropertyName= HidedName,Value=Secret,Route="InnerModel.HidedObject.HidedName" ]
How to get this information ?

You can write a method like this :
private static IEnumerable<PropInfo> GetPropertiesInfo(object obj, string route = "")
{
List<PropInfo> results = new List<PropInfo>();
// You can filter wich property you want https://learn.microsoft.com/en-us/dotnet/api/system.reflection.propertyinfo?view=net-6.0
var objectProperties = obj.GetType().GetProperties().Where(p => p.CanRead);
foreach (var property in objectProperties)
{
var value = property.GetValue(obj);
if (property.PropertyType.IsClass && property.PropertyType != typeof(string))
{
results.AddRange(GetPropertiesInfo(value, route + property.Name + "."));
}
else
{
// Check if the property has the Custom Attribute
var customAttributes = property.GetCustomAttributes<CustomAttribute>();
if (!customAttributes.Any())
continue;
// You can set a method in your Attribute : customAttributes.First().CheckIfNeedToStoreProperty(obj);
results.Add(new PropInfo()
{
PropertyName = property.Name,
Value = value,
Route = route + property.Name
});
}
}
return results;
}
public class PropInfo
{
public string PropertyName { get; set; }
public object Value { get; set; }
public string Route { get; set; }
}
public class CustomAttribute : Attribute
{
public bool CheckIfNeedToStoreProperty(object obj)
{
return true;
}
}

Deserialization contracts for properties

I need to deserialize jsons to a type that contains a property of interface type - IExceptionModel. I prescribe maps for interfaces to classes like this:
public static class JsonSerialization
{
public static T FromJson<T>(this string obj) => JsonConvert.DeserializeObject<T>(obj, Settings);
public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
{
ContractResolver = new ContractResolver()
};
private class ContractResolver : DefaultContractResolver
{
protected override JsonContract CreateContract(Type objectType)
{
var result = base.CreateContract(objectType);
if (objectType == typeof(IExceptionModel))
{
result.CreatedType = typeof(ExceptionModel);
result.DefaultCreator = () => result.CreatedType.GetConstructor(new Type[0]).Invoke(null);
}
return result;
}
}
}
Here are my interface and class types:
public interface IExceptionModel : IModelBase
{
public string Message { get; set; }
public int Index { get; set; }
}
public class ExceptionModel : IExceptionModel
{
public string Message { get ; set ; }
public byte Index { get; set; }
}
Here is the class to deserialize to:
public class Status
{
public IExceptionModel Error { get; set; }
}
When I take a proper input string like:
{
"Error" : {
"Message": "Error",
"Index": 404
}
}
and feed it to FromJson<Status> method, described above, I get Error property set to null, although I believe I have resolved the contract for the interface.
What else do I need to do in order to make it work?
Update.
When preparing this example, I messed some details. The IExceptionModel Error property doesn't have setter on the interface. It does on implementation. So now, when I have added setter to the interface, the property ends up with the needed value. If I wipe it, it has null after deserialization.
So the question turns into, how do I tell Newtonsoft Serializer to use the constructor of the implementation, use ITS getters and setters to fill what properties it can and only then treat it as the interface instance?
I found a workaround to assign an internal setter to the interface property and then instruct:
jsonContract.DefaultCreatorNonPublic = true;
But it makes the interface look crooked, to say the least.

I made some corrections and this worked for me:
result.CreatedType = typeof(Status); --> result.CreatedType = typeof(ExceptionModel);
public byte Index { get; set; } --> public int Index { get; set; }
I uploaded this online example: https://dotnetfiddle.net/ETSJee
using System;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
public interface IModelBase {}
public interface IExceptionModel : IModelBase
{
public string Message { get; set; }
public int Index { get; set; }
}
public class ExceptionModel : IExceptionModel
{
public string Message { get ; set ; }
public int Index { get; set; }
}
public class Status
{
public IExceptionModel Error { get; set; }
}
public static class JsonSerialization
{
public static T FromJson<T>(this string obj)
{
return JsonConvert.DeserializeObject<T>(obj, Settings);
}
public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
{
ContractResolver = new ContractResolver()
};
private class ContractResolver : DefaultContractResolver
{
protected override JsonContract CreateContract(Type objectType)
{
var result = base.CreateContract(objectType);
if (objectType == typeof(IExceptionModel))
{
result.CreatedType = typeof(ExceptionModel);
result.DefaultCreator = () => result.CreatedType.GetConstructor(new Type[0]).Invoke(null);
}
return result;
}
}
}
class Program
{
static void Main(string[] args)
{
var txt = #"
{
'Error' : {
'Message': 'Error',
'Index': 404
}
}
";
var obj = JsonSerialization.FromJson<Status>(txt);
Console.WriteLine(obj.Error.Index);
Console.WriteLine(obj.Error.Message);
}
}

this works for me without any contract resolvers
var status = JsonConvert.DeserializeObject<Status>(txt);
public class Status
{
public IExceptionModel Error { get; set; }
[JsonConstructor]
public Status (ExceptionModel error) {
Error=error;
}
public Status() {}
}
if you need to use it in many classes you can use this code instead
public class Status
{
[JsonProperty("Error")]
private ExceptionModel _error
{
set { Error = value; }
get { return (ExceptionModel)Error; }
}
[JsonIgnore]
public IExceptionModel Error { get; set; }
}
test
var status = JsonConvert.DeserializeObject<MyClass>(txt);
Console.WriteLine(status.Error.Index); //404
Console.WriteLine(status.Error.Message); //Error
public class MyClass:Status
{
public string Name {get; set;}
}

How to serialize different object level by jsonconvert

I got the object below
public class ResponseMessage
{
public string Code { get; set; }
public string Msg { get; set; }
public Person[] Data { get; set; }
}
public class Person
{
public string name { get; set; }
public string age { get; set; }
public PersonDetail Detail { get; set; }
}
public class PersonDetail
{
public string Birthday { get; set; }
public string CellPhone { get; set; }
}
How to generate different level by user privilege,like level 1
{"Code":"0000","Msg":"OK"}
,level 2
{"Code":"0000","Msg":"OK","Data":[{"Alex","25"},{"Ben","30"}]}
I have tried to using settings(MaxDepth),but it seems not work.....
Is there any way that can hide data dynamically?

Use Conditional Property Serialization.
You have two options for implementing it:
If ResponseMessage can be modified (i.e., you can add a method to it) and if it has access to privilege level (e.g., via function call), supply a ShouldSerialize method.
For example:
public class ResponseMessage
{
public string Code { get; set; }
public string Msg { get; set; }
public Person[] Data { get; set; }
public bool ShouldSerializeData()
{
// Privileger.GetPrivilege() is a naive example of a method
// that gets you privilige level
return Privileger.GetPrivilege() > 1;
}
}
If not, go with a custom ContractResolver.
Here's a simple one:
public class PrivilegeContractResolver : DefaultContractResolver
{
public int privilege = -1;
public PrivilegeContractResolver(int privilege)
{
this.privilege = privilege;
}
protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
{
JsonProperty property = base.CreateProperty(member, memberSerialization);
if (property.PropertyName == "Data")
{
property.ShouldSerialize = dummy => privilege > 1;
}
return property;
}
}
Example usage:
public void Run()
{
ResponseMessage r = new ResponseMessage
{
Code = "some_code",
Msg = "some_message",
Data = new [] { new Person { name = "Joe" } }
};
var lowPriv = JsonConvert.SerializeObject(r, new JsonSerializerSettings
{
ContractResolver = new PrivilegeContractResolver(0)
});
var highPriv = JsonConvert.SerializeObject(r, new JsonSerializerSettings
{
ContractResolver = new PrivilegeContractResolver(2)
});
Console.WriteLine(lowPriv); // outputs: {"Code":"some_code","Msg":"some_message"}
Console.WriteLine(highPriv); // outputs: {"Code":"some_code","Msg":"some_message","Data":[{"name":"Joe","age":null,"Detail":null}]}
}

How to configure JSON.net deserializer to track missing properties?

Sample class:
public class ClassA
{
public int Id { get; set; }
public string SomeString { get; set; }
public int? SomeInt { get; set; }
}
Default deserializer:
var myObject = JsonConvert.DeserializeObject<ClassA>(str);
Create the same object for two different inputs
{"Id":5}
or
{"Id":5,"SomeString":null,"SomeInt":null}
How can I track properties that were missing during deserialization process and preserve the same behavior? Is there a way to override some of JSON.net serializer methods (e.g. DefaultContractResolver class methods) to achive this. For example:
List<string> missingProps;
var myObject = JsonConvert.DeserializeObject<ClassA>(str, settings, missingProps);
For the first input list should contains the names of the missing properties ("SomeString", "SomeInt") and for second input it should be empty. Deserialized object remains the same.

1. JSON has a property which is missing in your class
Using property JsonSerializerSettings.MissingMemberHandling you can say whether missing properties are handled as errors.
Than you can install the Error delegate which will register errors.
This will detect if there is some "garbage" property in JSON string.
public class ClassA
{
public int Id { get; set; }
public string SomeString { get; set; }
}
internal class Program
{
private static void Main(string[] args)
{
const string str = "{'Id':5, 'FooBar': 42 }";
var myObject = JsonConvert.DeserializeObject<ClassA>(str
, new JsonSerializerSettings
{
Error = OnError,
MissingMemberHandling = MissingMemberHandling.Error
});
Console.ReadKey();
}
private static void OnError(object sender, ErrorEventArgs args)
{
Console.WriteLine(args.ErrorContext.Error.Message);
args.ErrorContext.Handled = true;
}
}
2. Your class has a property which is missing in JSON
Option 1:
Make it a required property:
public class ClassB
{
public int Id { get; set; }
[JsonProperty(Required = Required.Always)]
public string SomeString { get; set; }
}
Option 2:
Use some "special" value as a default value and check afterwards.
public class ClassB
{
public int Id { get; set; }
[DefaultValue("NOTSET")]
public string SomeString { get; set; }
public int? SomeInt { get; set; }
}
internal class Program
{
private static void Main(string[] args)
{
const string str = "{ 'Id':5 }";
var myObject = JsonConvert.DeserializeObject<ClassB>(str
, new JsonSerializerSettings
{
DefaultValueHandling = DefaultValueHandling.Populate
});
if (myObject.SomeString == "NOTSET")
{
Console.WriteLine("no value provided for property SomeString");
}
Console.ReadKey();
}
}
Option 3:
Another good idea would be to encapsulate this check iside the class istself. Create a Verify() method as shown below and call it after deserialization.
public class ClassC
{
public int Id { get; set; }
[DefaultValue("NOTSET")]
public string SomeString { get; set; }
public int? SomeInt { get; set; }
public void Verify()
{
if (SomeInt == null ) throw new JsonSerializationException("SomeInt not set!");
if (SomeString == "NOTSET") throw new JsonSerializationException("SomeString not set!");
}
}

Another way to find null/undefined tokens during De-serialization is to write a custom JsonConverter , Here is an example of custom converter which can report both omitted tokens (e.g. "{ 'Id':5 }") and null tokens (e.g {"Id":5,"SomeString":null,"SomeInt":null})
public class NullReportConverter : JsonConverter
{
private readonly List<PropertyInfo> _nullproperties=new List<PropertyInfo>();
public bool ReportDefinedNullTokens { get; set; }
public IEnumerable<PropertyInfo> NullProperties
{
get { return _nullproperties; }
}
public void Clear()
{
_nullproperties.Clear();
}
public override bool CanConvert(Type objectType)
{
return true;
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
existingValue = existingValue ?? Activator.CreateInstance(objectType, true);
var jObject = JObject.Load(reader);
var properties =
objectType.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
foreach (var property in properties)
{
var jToken = jObject[property.Name];
if (jToken == null)
{
_nullproperties.Add(property);
continue;
}
var value = jToken.ToObject(property.PropertyType);
if(ReportDefinedNullTokens && value ==null)
_nullproperties.Add(property);
property.SetValue(existingValue, value, null);
}
return existingValue;
}
//NOTE: we can omit writer part if we only want to use the converter for deserializing
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var objectType = value.GetType();
var properties =
objectType.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
writer.WriteStartObject();
foreach (var property in properties)
{
var propertyValue = property.GetValue(value, null);
writer.WritePropertyName(property.Name);
serializer.Serialize(writer, propertyValue);
}
writer.WriteEndObject();
}
}
Note: we can omit the Writer part if we don't need to use it for serializing objects.
Usage Example:
class Foo
{
public int Id { get; set; }
public string SomeString { get; set; }
public int? SomeInt { get; set; }
}
class Program
{
static void Main(string[] args)
{
var nullConverter=new NullReportConverter();
Console.WriteLine("Pass 1");
var obj0 = JsonConvert.DeserializeObject<Foo>("{\"Id\":5, \"Id\":5}", nullConverter);
foreach(var p in nullConverter.NullProperties)
Console.WriteLine(p);
nullConverter.Clear();
Console.WriteLine("Pass2");
var obj1 = JsonConvert.DeserializeObject<Foo>("{\"Id\":5,\"SomeString\":null,\"SomeInt\":null}" , nullConverter);
foreach (var p in nullConverter.NullProperties)
Console.WriteLine(p);
nullConverter.Clear();
nullConverter.ReportDefinedNullTokens = true;
Console.WriteLine("Pass3");
var obj2 = JsonConvert.DeserializeObject<Foo>("{\"Id\":5,\"SomeString\":null,\"SomeInt\":null}", nullConverter);
foreach (var p in nullConverter.NullProperties)
Console.WriteLine(p);
}
}

I got this problem, but defaultValue was not solution due to POCO object. I think this is simpler approach than NullReportConverter.
There are three unit tests. Root is class that encapsulate whole json. Key is type of the Property. Hope this helps someone.
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Newtonsoft.Json;
namespace SomeNamespace {
[TestClass]
public class NullParseJsonTest {
[TestMethod]
public void TestMethod1()
{
string slice = "{Key:{guid:\"asdf\"}}";
var result = JsonConvert.DeserializeObject<Root>(slice);
Assert.IsTrue(result.OptionalKey.IsSet);
Assert.IsNotNull(result.OptionalKey.Value);
Assert.AreEqual("asdf", result.OptionalKey.Value.Guid);
}
[TestMethod]
public void TestMethod2()
{
string slice = "{Key:null}";
var result = JsonConvert.DeserializeObject<Root>(slice);
Assert.IsTrue(result.OptionalKey.IsSet);
Assert.IsNull(result.OptionalKey.Value);
}
[TestMethod]
public void TestMethod3()
{
string slice = "{}";
var result = JsonConvert.DeserializeObject<Root>(slice);
Assert.IsFalse(result.OptionalKey.IsSet);
Assert.IsNull(result.OptionalKey.Value);
}
}
class Root {
public Key Key {
get {
return OptionalKey.Value;
}
set {
OptionalKey.Value = value;
OptionalKey.IsSet = true; // This does the trick, it is never called by JSON.NET if attribute missing
}
}
[JsonIgnore]
public Optional<Key> OptionalKey = new Optional<Key> { IsSet = false };
};
class Key {
public string Guid { get; set; }
}
class Optional<T> {
public T Value { get; set; }
public bool IsSet { get; set; }
}
}

MVC 3 model binding with underscores

I'm posting json with variables names with underscores (like_this) and attempting to bind to a model that is camelcased (LikeThis), but the values are unable to be bound.
I know I could write a custom model binder, but since the underscored convention is so common I'd expect that a solution already existed.
The action/model I'm trying to post to is:
/* in controller */
[HttpPost]
public ActionResult UpdateArgLevel(UserArgLevelModel model) {
// do something with the data
}
/* model */
public class UserArgLevelModel {
public int Id { get; set; }
public string FirstName { get; set; }
public string Surname { get; set; }
public int ArgLevelId { get; set; }
}
and the json data is like:
{
id: 420007,
first_name: "Marc",
surname: "Priddes",
arg_level_id: 4
}
(Unfortunately I can't change either the naming of either the json or the model)

You can start writing a custom Json.NET ContractResolver:
public class DeliminatorSeparatedPropertyNamesContractResolver :
DefaultContractResolver
{
private readonly string _separator;
protected DeliminatorSeparatedPropertyNamesContractResolver(char separator)
: base(true)
{
_separator = separator.ToString();
}
protected override string ResolvePropertyName(string propertyName)
{
var parts = new List<string>();
var currentWord = new StringBuilder();
foreach (var c in propertyName)
{
if (char.IsUpper(c) && currentWord.Length > 0)
{
parts.Add(currentWord.ToString());
currentWord.Clear();
}
currentWord.Append(char.ToLower(c));
}
if (currentWord.Length > 0)
{
parts.Add(currentWord.ToString());
}
return string.Join(_separator, parts.ToArray());
}
}
This is for your particular case, becase you need a snake case ContractResolver:
public class SnakeCasePropertyNamesContractResolver :
DeliminatorSeparatedPropertyNamesContractResolver
{
public SnakeCasePropertyNamesContractResolver() : base('_') { }
}
Then you can write a custom attribute to decorate your controller actions:
public class JsonFilterAttribute : ActionFilterAttribute
{
public string Parameter { get; set; }
public Type JsonDataType { get; set; }
public JsonSerializerSettings Settings { get; set; }
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
if (filterContext.HttpContext.Request.ContentType.Contains("application/json"))
{
string inputContent;
using (var reader = new StreamReader(filterContext.HttpContext.Request.InputStream))
{
inputContent = reader.ReadToEnd();
}
var result = JsonConvert.DeserializeObject(inputContent, JsonDataType, Settings ?? new JsonSerializerSettings());
filterContext.ActionParameters[Parameter] = result;
}
}
}
And finally:
[JsonFilter(Parameter = "model", JsonDataType = typeof(UserArgLevelModel), Settings = new JsonSerializerSettings { ContractResolver = new SnakeCasePropertyNamesContractResolver() })]
public ActionResult UpdateArgLevel(UserArgLevelModel model) {
{
// model is deserialized correctly!
}