Dynamically add properties to a existing object

Question

I create the person object like this    Person person new Person  Sam   Lewis      It has properties like this   person Dob person Address   But now I want to add properties like this and set the values at the run time after creating the object  person Age person Sex  How can I add those extra properties after creating the object  Those property name can be changed time to time  Therefor can t hardcode the  Age  and  Sex

User · Answer

If you only need the dynamic properties for JSON serialization/deserialization, eg if your API accepts a JSON object with different fields depending on context, then you can use the JsonExtensionData attribute available in Newtonsoft.Json or System.Text.Json.

Example:

public class Pet
{
    public string Name { get; set; }
    public string Type { get; set; }

    [JsonExtensionData]
    public IDictionary<string, object> AdditionalData { get; set; }
}

Then you can deserialize JSON:

public class Program
{
    public static void Main()
    {
        var bingo = JsonConvert.DeserializeObject<Pet>("{\"Name\": \"Bingo\", \"Type\": \"Dog\", \"Legs\": 4 }");
        Console.WriteLine(bingo.AdditionalData["Legs"]);        // 4

        var tweety = JsonConvert.DeserializeObject<Pet>("{\"Name\": \"Tweety Pie\", \"Type\": \"Bird\", \"CanFly\": true }");
        Console.WriteLine(tweety.AdditionalData["CanFly"]);     // True

        tweety.AdditionalData["Color"] = "#ffff00";

        Console.WriteLine(JsonConvert.SerializeObject(tweety)); // {"Name":"Tweety Pie","Type":"Bird","CanFly":true,"Color":"#ffff00"}
    }
}

User · Answer

It s not possible with a  normal  object  but you can do it with an ExpandoObject and the dynamic keyword   dynamic person   new ExpandoObject    person FirstName    Sam   person LastName    Lewis   person Age   42  person Foo    Bar         If you try to assign a property that doesn t exist  it is added to the object  If you try to read a property that doesn t exist  it will raise an exception  So it s roughly the same behavior as a dictionary  and ExpandoObject actually implements IDictionary lt string  object gt

User · Answer

Take a look at the ExpandoObject   For example   dynamic person   new ExpandoObject    person Name    Mr bar   person Sex    No Thanks   person Age   123    Additional reading here

User · Answer

Take a look at the Clay library   http   clay codeplex com   It provides something similar to the ExpandoObject but with a bunch of extra features  Here is blog post explaining how to use it   http   weblogs asp net bleroy archive 2010 08 18 clay-malleable-c-dynamic-objects-part-2 aspx   be sure to read the IPerson interface example

User · Answer

If you can t use the dynamic type with ExpandoObject  then you could use a  Property Bag  mechanism  where  using a dictionary  or some other key   value collection type  you store string key s that name the properties and values of the required type   See here for an example implementation

User · Answer

Consider using the decorator pattern http   en wikipedia org wiki Decorator pattern  You can change the decorator at runtime with one that has different properties when an event occurs

User · Answer

If you have a class with an object property  or if your property actually casts to an object  you can reshape the object by reassigning its properties  as in     MyClass varClass   new MyClass      varClass propObjectProperty   new   Id   1  Description    test          if you need to treat the class as an object   var varObjectProperty     dynamic varClass  propObjectProperty      dynamic varClass  propObjectProperty   new   Id   varObjectProperty Id  Description   varObjectProperty Description  NewDynamicProperty    new dynamic property description          if your property is an object  instead   var varObjectProperty   varClass propObjectProperty    varClass propObjectProperty   new   Id     dynamic varObjectProperty  Id  Description     dynamic varObjectProperty  Description  NewDynamicProperty    new dynamic property description        With this approach  you basically rewrite the object property adding or removing properties as if you were first creating the object with the  new           syntax   In your particular case  you re probably better off creating an actual object to which you assign properties like  dob  and  address  as if it were a person  and at the end of the process  transfer the properties to the actual  Person  object

[c#] Dynamically add properties to a existing object

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