using System;

using System.Text.Json;

using System.Text.Json.Serialization;

​

public class Program

{

    public static void Main()

    {

        var x = new Sample();

        Console.WriteLine("Initial Values");

        Console.WriteLine("A: " + x.A);

        Console.WriteLine("A: " + x.A);

        Console.WriteLine("\nRunning Method");

        Console.WriteLine("TestUpdateA(): " + x.TestUpdateA());

        Console.WriteLine("\nResult");

        Console.WriteLine("A: " + x.A);

        Console.WriteLine("B: " + x.B);

    }

}

​

public class Sample

{

    public string A = null;

    public string B = "VALUE";

    public string TestUpdateA()

    {

        return A ??= B;

    }

}