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List to JSON with JsonSerializer.Serializer returns null

I have a class named clsTest which is defined as:
public class clsTest
{
public string Name;
public string Family;
public int Age;
}
I have another class named clsMain which is Serializing three instances of clsTest class to JSON as:
public class clsMain
{
public string mtdMain()
{
clsTest ct1_a = new clsTest();
clsTest ct1_b = new clsTest();
clsTest ct1_c = new clsTest();
ct1_a.Name = "Satoshi";
ct1_a.Family = "Nakamato";
ct1_b.Name = "Charles";
ct1_b.Family = "Hoskinson";
ct1_b.Age = 33;
ct1_c.Name = "AmirAli";
ct1_c.Family = "Sam";
ct1_c.Age = 25;
List<clsTest> lst = new List<clsTest>();
lst.Add(ct1_a);
lst.Add(ct1_b);
lst.Add(ct1_c);
JsonSerializerOptions option = new JsonSerializerOptions();
option.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
option.Converters.Add(new JsonStringEnumConverter(JsonNamingPolicy.CamelCase));
return JsonSerializer.Serialize(lst, option);
}
}
When I debug the project my list is full as shown in the screenshot:
But at the end return JsonSerializer.Serialize(lst, option); serialize as below:
I couldn't find the problem, any suggestion will be appreciated.
Thanks.

Use properties instead of fields, like so:
public class Test
{
public string Name { get; set; }
public string Family { get; set; }
public int Age { get; set; }
}

C# Accessing custom attribute of owner object

How can I access the custom attribute of the parent or owner object.
Look at the FieldInfo property of the SQLFieldInfo struct
Here's a more detailed program that will compile and run that shows what I need.
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
Employee myclass = new Employee();
// Load from sql server...
myclass.Name = "Alain";
myclass.Age = 51;
//----
MessageBox.Show(myclass.Name.ToString()); // Should return Alain
MessageBox.Show(myclass.Age.FieldInfo.Type.ToString()); // Should output "int"
}
}
// This next class is generated by a helper exe that reads SQL table design and create the class from it
[SQLTableAttribute(DatabaseName = "Employees", Schema = "dbo", TableName = "Employees")]
public class Employee
{
[SQLFieldAttribute(FieldName = "ID", Type = SqlDbType.Int)]
public SQLFieldInfo<int> ID { get; set; }
[SQLFieldAttribute(FieldName = "Name", Type = SqlDbType.NVarChar, Size = 200)]
public SQLFieldInfo<String> Name { get; set; }
[SQLFieldAttribute(FieldName = "Age", Type = SqlDbType.Int)]
public SQLFieldInfo<int> Age { get; set; }
}
public struct SQLFieldInfo<T>
{
private readonly T value;
public SQLFieldInfo(T Value)
{
this.value = Value;
}
public static implicit operator SQLFieldInfo<T>(T Value)
{
return new SQLFieldInfo<T>(Value);
}
public T Value
{
get
{
return this.value;
}
}
public override string ToString()
{
return this.value.ToString();
}
public SQLFieldAttribute FieldInfo
{
get
{
// Need to retreive the attribute class of the parent or declaring member
return null;
}
}
}
// Holds the sql field information
public class SQLFieldAttribute : Attribute
{
public string FieldName { get; set; }
public SqlDbType Type { get; set; }
public bool AllowNull { get; set; }
public int Size { get; set; }
}
// Holds the sql table information
public class SQLTableAttribute : Attribute
{
public string DatabaseName { get; set; }
public string Schema { get; set; } = "dbo";
public string TableName { get; set; }
}
Thank you!
Alain

My data class is as follows (should be fairly translatable to A above):
public class Foo
{
[Argument(Help = "Name", AssignmentDelimiter = "=")]
public string Name
{
get;
set;
}
}
A helper class is responsible of reading attribute values of objects:
static public string GetCommandLineDelimiter<T>(Expression<Func<T>> property)
{
if(property != null)
{
var memberExpression = (MemberExpression)property.Body;
string propertyName = memberExpression.Member.Name;
PropertyInfo prop = typeof(Arguments).GetProperty(propertyName);
if(prop != null)
{
object[] dbFieldAtts = prop.GetCustomAttributes(typeof(ArgumentAttribute), true);
if(dbFieldAtts.Length > 0)
{
return ((ArgumentAttribute)dbFieldAtts[0]).AssignmentDelimiter;
}
}
}
return null;
}
To use it, simply:
string delimiter = GetCommandLineDelimiter(() => myObject.Name);
That will get the attribute value of AssignmentDelimiter on property Name, i.e. "=".

First, MSDN is your friend.
Then, if you want to get the attributes for ancestors just specify true in the inherit flag of the method:
var attribute = typeof(A).GetProperty("myprop").GetCustomAttributes(true)
.OfType<MycustomAttrib>().FirstOrDefault();

This works. I am doing a lazy initialization of a reference to the custom attribute by using reflection to look at all the properties of all the types.
public class MycustomAttribAttribute : Attribute
{
public MycustomAttribAttribute(string name)
{
this.Name=name;
}
public string Name { get; private set; }
}
class A
{
public A() { MyProp=new B(); }
[MycustomAttrib(name: "OK")]
public B MyProp { get; set; }
}
class B
{
private static Lazy<MycustomAttribAttribute> att = new Lazy<MycustomAttribAttribute>(() =>
{
var types = System.Reflection.Assembly.GetExecutingAssembly().DefinedTypes;
foreach(var item in types)
{
foreach(var prop in item.DeclaredProperties)
{
var attr = prop.GetCustomAttributes(typeof(MycustomAttribAttribute), false);
if(attr.Length>0)
{
return attr[0] as MycustomAttribAttribute;
}
}
}
return null;
});
public string MyProp2
{
get
{
return att.Value.Name;
}
}
}
class Program
{
static void Main(string[] args)
{
// Finds the attribute reference and returns "OK"
string name = (new A()).MyProp.MyProp2;
// Uses the stored attribute reference to return "OK"
string name2 = (new A()).MyProp.MyProp2;
}
}

Inheritance from Jobject Newtonsoft

Inheritance from Jobject(Newtonsoft) the existents properties from class not serialized.
Why were the Id and Name properties not serialized?
public class Test : JObject
{
public int Id { get; set; }
public string Name { get; set; }
}
class Program
{
static void Main(string[] args)
{
var test = new Test();
test["new_pro"] = 123456;
test.Id = 1;
test.Name = "Dog";
var r = Newtonsoft.Json.JsonConvert.SerializeObject(test);
// Result = { "new_pro":123456}
}
}
Any idea?

Whatever is the reason you want to do that - the reason is simple: JObject implements IDictionary and this case is treated in a special way by Json.NET. If your class implements IDictionary - Json.NET will not look at properties of your class but instead will look for keys and values in the dictionary. So to fix your case you can do this:
public class Test : JObject
{
public int Id
{
get { return (int) this["id"]; }
set { this["id"] = value; }
}
public string Name
{
get { return (string) this["name"]; }
set { this["name"] = value; }
}
}
If you just want to have both dynamic and static properties on your object - there is no need to inherit from JObject. Instead, use JsonExtensionData attribute:
public class Test {
public int Id { get; set; }
public string Name { get; set; }
[JsonExtensionData]
public Dictionary<string, JToken> AdditionalProperties { get; set; } = new Dictionary<string, JToken>();
}
var test = new Test();
test.AdditionalProperties["new_pro"] = 123456;
test.Id = 1;
test.Name = "Dog";
var r = Newtonsoft.Json.JsonConvert.SerializeObject(test);

Newtonsoft JSON dynamic property name

Is there a way to change name of Data property during serialization, so I can reuse this class in my WEB Api.
For an example, if i am returning paged list of users, Data property should be serialized as "users", if i'm returning list of items, should be called "items", etc.
Is something like this possible:
public class PagedData
{
[JsonProperty(PropertyName = "Set from constructor")]??
public IEnumerable<T> Data { get; private set; }
public int Count { get; private set; }
public int CurrentPage { get; private set; }
public int Offset { get; private set; }
public int RowsPerPage { get; private set; }
public int? PreviousPage { get; private set; }
public int? NextPage { get; private set; }
}
EDIT:
I would like to have a control over this functionality, such as passing name to be used if possible. If my class is called UserDTO, I still want serialized property to be called Users, not UserDTOs.
Example
var usersPagedData = new PagedData("Users", params...);

You can do this with a custom ContractResolver. The resolver can look for a custom attribute which will signal that you want the name of the JSON property to be based on the class of the items in the enumerable. If the item class has another attribute on it specifying its plural name, that name will then be used for the enumerable property, otherwise the item class name itself will be pluralized and used as the enumerable property name. Below is the code you would need.
First let's define some custom attributes:
public class JsonPropertyNameBasedOnItemClassAttribute : Attribute
{
}
public class JsonPluralNameAttribute : Attribute
{
public string PluralName { get; set; }
public JsonPluralNameAttribute(string pluralName)
{
PluralName = pluralName;
}
}
And then the resolver:
public class CustomResolver : DefaultContractResolver
{
protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
{
JsonProperty prop = base.CreateProperty(member, memberSerialization);
if (prop.PropertyType.IsGenericType && member.GetCustomAttribute<JsonPropertyNameBasedOnItemClassAttribute>() != null)
{
Type itemType = prop.PropertyType.GetGenericArguments().First();
JsonPluralNameAttribute att = itemType.GetCustomAttribute<JsonPluralNameAttribute>();
prop.PropertyName = att != null ? att.PluralName : Pluralize(itemType.Name);
}
return prop;
}
protected string Pluralize(string name)
{
if (name.EndsWith("y") && !name.EndsWith("ay") && !name.EndsWith("ey") && !name.EndsWith("oy") && !name.EndsWith("uy"))
return name.Substring(0, name.Length - 1) + "ies";
if (name.EndsWith("s"))
return name + "es";
return name + "s";
}
}
Now you can decorate the variably-named property in your PagedData<T> class with the [JsonPropertyNameBasedOnItemClass] attribute:
public class PagedData<T>
{
[JsonPropertyNameBasedOnItemClass]
public IEnumerable<T> Data { get; private set; }
...
}
And decorate your DTO classes with the [JsonPluralName] attribute:
[JsonPluralName("Users")]
public class UserDTO
{
...
}
[JsonPluralName("Items")]
public class ItemDTO
{
...
}
Finally, to serialize, create an instance of JsonSerializerSettings, set the ContractResolver property, and pass the settings to JsonConvert.SerializeObject like so:
JsonSerializerSettings settings = new JsonSerializerSettings
{
ContractResolver = new CustomResolver()
};
string json = JsonConvert.SerializeObject(pagedData, settings);
Fiddle: https://dotnetfiddle.net/GqKBnx
If you're using Web API (looks like you are), then you can install the custom resolver into the pipeline via the Register method of the WebApiConfig class (in the App_Start folder).
JsonSerializerSettings settings = config.Formatters.JsonFormatter.SerializerSettings;
settings.ContractResolver = new CustomResolver();
Another Approach
Another possible approach uses a custom JsonConverter to handle the serialization of the PagedData class specifically instead using the more general "resolver + attributes" approach presented above. The converter approach requires that there be another property on your PagedData class which specifies the JSON name to use for the enumerable Data property. You could either pass this name in the PagedData constructor or set it separately, as long as you do it before serialization time. The converter will look for that name and use it when writing out JSON for the enumerable property.
Here is the code for the converter:
public class PagedDataConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType.IsGenericType && objectType.GetGenericTypeDefinition() == typeof(PagedData<>);
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
Type type = value.GetType();
var bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public;
string dataPropertyName = (string)type.GetProperty("DataPropertyName", bindingFlags).GetValue(value);
if (string.IsNullOrEmpty(dataPropertyName))
{
dataPropertyName = "Data";
}
JObject jo = new JObject();
jo.Add(dataPropertyName, JArray.FromObject(type.GetProperty("Data").GetValue(value)));
foreach (PropertyInfo prop in type.GetProperties().Where(p => !p.Name.StartsWith("Data")))
{
jo.Add(prop.Name, new JValue(prop.GetValue(value)));
}
jo.WriteTo(writer);
}
public override bool CanRead
{
get { return false; }
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
To use this converter, first add a string property called DataPropertyName to your PagedData class (it can be private if you like), then add a [JsonConverter] attribute to the class to tie it to the converter:
[JsonConverter(typeof(PagedDataConverter))]
public class PagedData<T>
{
private string DataPropertyName { get; set; }
public IEnumerable<T> Data { get; private set; }
...
}
And that's it. As long as you've set the DataPropertyName property, it will be picked up by the converter on serialization.
Fiddle: https://dotnetfiddle.net/8E8fEE

UPD Sep 2020: #RyanHarlich pointed that proposed solution doesn't work out of the box. I found that Newtonsoft.Json doesn't initialize getter-only properties in newer versions, but I'm pretty sure it did ATM I wrote this answer in 2016 (no proofs, sorry :).
A quick-n-dirty solution is to add public setters to all properties ( example in dotnetfiddle ). I encourage you to find a better solution that keeps read-only interface for data objects. I haven't used .Net for 3 years, so cannot give you that solution myself, sorry :/
Another option with no need to play with json formatters or use string replacements - only inheritance and overriding (still not very nice solution, imo):
public class MyUser { }
public class MyItem { }
// you cannot use it out of the box, because it's abstract,
// i.e. only for what's intended [=implemented].
public abstract class PaginatedData<T>
{
// abstract, so you don't forget to override it in ancestors
public abstract IEnumerable<T> Data { get; }
public int Count { get; }
public int CurrentPage { get; }
public int Offset { get; }
public int RowsPerPage { get; }
public int? PreviousPage { get; }
public int? NextPage { get; }
}
// you specify class explicitly
// name is clear,.. still not clearer than PaginatedData<MyUser> though
public sealed class PaginatedUsers : PaginatedData<MyUser>
{
// explicit mapping - more agile than implicit name convension
[JsonProperty("Users")]
public override IEnumerable<MyUser> Data { get; }
}
public sealed class PaginatedItems : PaginatedData<MyItem>
{
[JsonProperty("Items")]
public override IEnumerable<MyItem> Data { get; }
}

Here is a solution that doesn't require any change in the way you use the Json serializer. In fact, it should also work with other serializers. It uses the cool DynamicObject class.
The usage is just like you wanted:
var usersPagedData = new PagedData<User>("Users");
....
public class PagedData<T> : DynamicObject
{
private string _name;
public PagedData(string name)
{
if (name == null)
throw new ArgumentNullException(nameof(name));
_name = name;
}
public IEnumerable<T> Data { get; private set; }
public int Count { get; private set; }
public int CurrentPage { get; private set; }
public int Offset { get; private set; }
public int RowsPerPage { get; private set; }
public int? PreviousPage { get; private set; }
public int? NextPage { get; private set; }
public override IEnumerable<string> GetDynamicMemberNames()
{
yield return _name;
foreach (var prop in GetType().GetProperties().Where(p => p.CanRead && p.GetIndexParameters().Length == 0 && p.Name != nameof(Data)))
{
yield return prop.Name;
}
}
public override bool TryGetMember(GetMemberBinder binder, out object result)
{
if (binder.Name == _name)
{
result = Data;
return true;
}
return base.TryGetMember(binder, out result);
}
}

The following is another solution tested in .NET Standard 2.
public class PagedResult<T> where T : class
{
[JsonPropertyNameBasedOnItemClassAttribute]
public List<T> Results { get; set; }
[JsonProperty("count")]
public long Count { get; set; }
[JsonProperty("total_count")]
public long TotalCount { get; set; }
[JsonProperty("current_page")]
public long CurrentPage { get; set; }
[JsonProperty("per_page")]
public long PerPage { get; set; }
[JsonProperty("pages")]
public long Pages { get; set; }
}
I am using Humanizer for pluralization.
protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
{
JsonProperty property = base.CreateProperty(member, memberSerialization);
if (member.GetCustomAttribute<JsonPropertyNameBasedOnItemClassAttribute>() != null)
{
Type[] arguments = property.DeclaringType.GenericTypeArguments;
if(arguments.Length > 0)
{
string name = arguments[0].Name.ToString();
property.PropertyName = name.ToLower().Pluralize();
}
return property;
}
return base.CreateProperty(member, memberSerialization);
}

There's a package called SerializationInterceptor. Here's the GitHub link: https://github.com/Dorin-Mocan/SerializationInterceptor/wiki. You can also install the package using Nuget Package Manager.
The example from below uses Syste.Text.Json for serialization. You can use any other serializer(except Newtonsoft.Json). For more info on why Newtonsoft.Json not allowed, please refer to GitHub documentation.
You can create an interceptor
public class JsonPropertyNameInterceptorAttribute : InterceptorAttribute
{
public JsonPropertyNameInterceptorAttribute(string interceptorId)
: base(interceptorId, typeof(JsonPropertyNameAttribute))
{
}
protected override void Intercept(in AttributeParams originalAttributeParams, object context)
{
string theNameYouWant;
switch (InterceptorId)
{
case "some id":
theNameYouWant = (string)context;
break;
default:
return;
}
originalAttributeParams.ConstructorArgs.First().ArgValue = theNameYouWant;
}
}
And put the interceptor on the Data prop
public class PagedData<T>
{
[JsonPropertyNameInterceptor("some id")]
[JsonPropertyName("during serialization this value will be replaced with the one passed in context")]
public IEnumerable<T> Data { get; private set; }
public int Count { get; private set; }
public int CurrentPage { get; private set; }
public int Offset { get; private set; }
public int RowsPerPage { get; private set; }
public int? PreviousPage { get; private set; }
public int? NextPage { get; private set; }
}
And then you can serialize the object like this
var serializedObj = InterceptSerialization(
obj,
objType,
(o, t) =>
{
return JsonSerializer.Serialize(o, t, new JsonSerializerOptions { ReferenceHandler = ReferenceHandler.Preserve });
},
context: "the name you want");
Hope this will be of use to you.

have a look here:
How to rename JSON key
Its not done during serialization but with a string operation.
Not very nice (in my eyes) but at least a possibility.
Cheers Thomas

How to auto-ignore all properties with no corresponding constructor parameter when serializing

Is there some non-attribute-based method of ignoring all properties that don't have a corresponding constructor parameter when serializing? For example, when serializing this class, property Combo should be ignored. A round-trip serialization/deserialization of an instance of MyClass doesn't require Combo to be serialized. Ideally I could use some out-of-the-box setting.
public class MyClass
{
public MyClass(int myInt, string myString)
{
this.MyInt = myInt;
this.MyString = myString;
}
public int MyInt { get; }
public string MyString { get; }
public string Combo => this.MyInt + this.MyString;
}

You can do this with a custom IContractResolver:
public class ConstructorPropertiesOnlyContractResolver : DefaultContractResolver
{
readonly bool serializeAllWritableProperties;
public ConstructorPropertiesOnlyContractResolver(bool serializeAllWritableProperties)
: base()
{
this.serializeAllWritableProperties = serializeAllWritableProperties;
}
protected override JsonObjectContract CreateObjectContract(Type objectType)
{
var contract = base.CreateObjectContract(objectType);
if (contract.CreatorParameters.Count > 0)
{
foreach (var property in contract.Properties)
{
if (contract.CreatorParameters.GetClosestMatchProperty(property.PropertyName) == null)
{
if (!serializeAllWritableProperties || !property.Writable)
property.Readable = false;
}
}
}
return contract;
}
}
Then use it like:
var settings = new JsonSerializerSettings { ContractResolver = new ConstructorPropertiesOnlyContractResolver(false) };
var json = JsonConvert.SerializeObject(myClass, Formatting.Indented, settings );
Pass true for serializeAllWritableProperties if you also want to serialize read/write properties that are not included in the constructor parameter list, e.g. AnUnrelatedReadWriteProperty in:
public class MyClass
{
public MyClass(int myInt, string myString)
{
this.MyInt = myInt;
this.MyString = myString;
}
public int MyInt { get; private set; }
public string MyString { get; private set; }
public string Combo { get { return this.MyInt + this.MyString; } }
public string AnUnrelatedReadWriteProperty { get; set; }
}
Note you may want to cache your contract resolver for best performance.