So I've been trying to play around little bit with a NuGet package called

But why are the values not applied to the variable "clonedPerson" afterwards?

CodePudding user response：

As your code is currently written, you are assigning a complete new object to your destination parameter. But this does not change the object you passed into that parameter. To overcome this issue there are several possibilites (in order of my personal preference)

1. You can just define PerformDeepCloning to return a Person

    public static Person PerformDeepCloning(Person source)
    {
      //call a method from the package
      Person destination = source.DeepClone();
      //this works fine
      Console.WriteLine("DEEP CLONED NAME = "   destination.Name);
      return destination;
    }
   

   and call it like this

    Person otherPerson = PerformDeepCloning(person);
   

   This would seem the most natural way for me to do it, instead of populating out or ref parameters of a method returning void, why not just return the result via return keyword?

2. Use the out keyword which was specifically designed for such situations (ie creating a new object inside the called method and pass it to the caller if return isn't possible for whatever resons)

    public static void PerformDeepCloning(Person source, out Person destination)
    {
      //call a method from the package
      destination = source.DeepClone();
      //this works fine
      Console.WriteLine("DEEP CLONED NAME = "   destination.Name);
    }
   

   and then call it like this

    //you must not assign a value here, when using the out keyword        
    Person otherPerson;
    PerformDeepCloning(person, out otherPerson);
   

   or starting with C#7 you can also use an inline declaration

    //no need to delare Person otherPerson; prior to the call
    PerformDeepCloning(person, out Person otherPerson);
   

3. Use the ref keyword which is capable of updating the reference which was passed in.

    public static void PerformDeepCloning(Person source, ref Person destination)
    {
      //call a method from the package
      destination = source.DeepClone();
      //this works fine
      Console.WriteLine("DEEP CLONED NAME = "   destination.Name);
    }
   

   and then call it like this

    Person otherPerson = new Person(); 
    PerformDeepCloning(person, ref otherPerson);
   

   But as you are creating a new instance of a Person anyways, you don't need to create a new object before the call (because this will be thrown away immediately) but initialize the otherPerson with null. But then you of course have to sure, you don't access otherPerson's properties, before you created an instance.

    Person otherPerson = null; 
    PerformDeepCloning(person, ref otherPerson);