ref and structs modification example

main.cs

// For more info on how to use ref keywords for modifying structs
// https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/ref

using System;

class MainClass {

  public class MyClass {
    public float number = 0;
  }

  // Structs can't be initialized
  public struct MyStruct {
    public float number;
  }

  // Class instances are passed as reference value, so they are mutable within the function context
  // and changes propagate to the original object
  public static void AddToClass(MyClass thing){
    thing.number++;
  }

  // Struct instances are passed as new values, so they are immutable and changes do not propagate
  // to the original object
  public static void AddToStructNoRef(MyStruct thing) {
    thing.number++;
  }

  // ref keyword allows structs to be passed as reference value instead, allowing mutability of the
  // original object
  public static void AddToStructWithRef(ref MyStruct thing) {
    thing.number++;
  }

  public static void Main (string[] args) {
    MyClass myInstance = new MyClass();
    MyStruct myThing = new MyStruct();

    Console.WriteLine ("myInstance.number before adding = " + myInstance.number);
    AddToClass(myInstance);
    Console.WriteLine ("myInstance.number after adding = " + myInstance.number);

    Console.WriteLine ("myThing.number before adding without ref = " + myThing.number);
    AddToStructNoRef(myThing);
    Console.WriteLine ("myThing.number after adding without ref = " + myThing.number);
    // ref keyword is used to indicate that the struct instance is passed as reference value
    AddToStructWithRef(ref myThing);
    Console.WriteLine ("myInstance.number after adding with ref = " + myInstance.number);
  }
}