test.cs

using System;

public class Program
{
  static int i = 0;
  static Test test = new Test();
  static Test GetTest => (i % 2) == 0 ? null : test;

  static string FuncWithSideEffect() {
    Console.WriteLine("Called inner");
    return "inner";
  }

  public static void Main()
  {
    Console.WriteLine("Started");
    Console.WriteLine("GetTest: {0}", GetTest);

    GetTest?.Func(FuncWithSideEffect());
    GetTest?.Func($"{test}");

    i = 1;
    Console.WriteLine("===");
    Console.WriteLine("GetTest: {0}", GetTest);

    GetTest?.Func(FuncWithSideEffect());
    GetTest?.Func($"{test}");

    i = 2;
    Console.WriteLine("===");
    Console.WriteLine("GetTest: {0}", GetTest);

    GetTest?.Func(FuncWithSideEffect());
    GetTest?.Func($"{test}");

    Console.WriteLine("Done");
  }
}


class Test {
  public void Func(string s) {
    Console.WriteLine("Called Func({0})", s);
  }

  public override string ToString() {
    Console.WriteLine("ToString called");
    return "test";
  }
}