C#：从子类继承到基类

Question

so I have a problem: When I'm trying to hand over a parameter from the Child-Class to the Base-Class, the parameter is not in the Base-Class:

public class Zeiteinheit : Shutdown_Time
{
     public int Public_minuten
     {
        get { return _minuten; }
        set { _minuten = value; }
     }

    public void Minuten_Zu_Sekunden_Umrechnung()
    {
        _sekunden = (_minuten * 60); 
    } 
}

public class Shutdown_Time
{
    protected int _sekunden;
    protected string herunterfahrenTimer;

    public string Public_herunterfahrenTimer 
    {
        get { return herunterfahrenTimer; }

        set { herunterfahrenTimer = $"-s -t {_sekunden}"; }
    }
}

MainClass:

//Umrechnung der eingetragenen Zeit findet statt
obj_zeiteinheit.Minuten_Zu_Sekunden_Umrechnung();

//Herunterfahren mit der Umgerechneten Zeit von stunden in sekunden
System.Diagnostics.Process.Start("Shutdown", obj_shutdown_Time.Public_herunterfahrenTimer);
break;

Result of an debug

My Question is here, did i missunderstood something by the concept of inheriting or what is my mistake?

(Sorry for my very bad english, and thanks for the help!)

Answer 1

You seem to be asking "when I set a property or field in a base class, how do I trigger the updating of a property or field in a derived class?"

But then you showed code that outlines you want to set ZeitenHeit.Public_Minuten = 60 , which does set _sekunden = 3600 but you then also want to update, in the same class , herunterfahrenTimer so it is -s -t 3600 because right now it isn't updated (the screenshot is null)

There is a small but critical difference between what you asked and what you appear to be trying to do, so you've essentially asked two questions. I'll deal with that one in the question title first:

how can a base class update a derived(child) class?

It can't; it doesn't even know it exists. The derived class knows the base class exists though, so you can use that instead

One way is to have the derived class override the setting function of the base class:

class MyBase{
  int _myField;

  virtual void SetMyField(int val){
    _myField = val;
  }
}

class MyDerived:MyBase{
  string _myOtherField;

  override void SetMyField(int val){
    base.SetMyField(val);
    _myOtherField = val.ToString();
  }
}

In use, a variable of type MyBase holding an instance of type MyDerived, will set both values when you call SetMyField:

var mb = new MyDerived();
mb.SetMyField(1); //implementation on MyDerived is used, causing _myOtherField to be set

---

You might have the base class raise an event (or invoke a delegate) when it's property is set and the derived class subscribes to it

class MyBase{
  int _myField;
  event EventHandler<int> MyFieldUpdatedTo;

  void SetMyField(int val){
    _myField = val;
    var e = MyFieldUpdatedTo;
    e?.Invoke(this, val);
  }
}

class MyDerived:MyBase{
  string _myOtherField;

  MyDerived(){ //constructor, or can also subscribe to event in the place that instantiates the MyDerived
    base.MyFieldUpdatedTo += val => _myOtherField = val.ToString(); 
  }
}

This is perhaps slightly unusual, though common to see in windows forms

However you arrange it, you need to leverage that the derived knows about the base but not the other way round, so anything done to the base needs to go via the derived, or via something that knows about both of them, or by creating a link from base to derived

---

In your specific case you're having a problem because the class that knows about both of your data items (the base class) only sets one of them

You could literally trigger the setting of the string by changing the value of the Public_herunterfahrenTimer to anything:

public void Minuten_Zu_Sekunden_Umrechnung()
{
    _sekunden = (_minuten * 60); 
    Public_herunterfahrenTimer = ""; //any string, the value is not used
} 

^{You could also put the setting of _sekunden into Public_herunterfahrenTimer and then set that property in the derived method}

But structuring the code like this, and actually the code structure in general is very strange- we simply wouldn't write code like that. There is no need for a string property that duplicates information that is remembered in the _sekunden variable, and does do on the set , which naturally allows data to go out of sync

Instead you should perhaps just calculate the string in a get :

public class Zeiteinheit : ShutdownTime
{
     public int Minuten
     {
        get { return _sekunden / 60; }
        set { _sekunden = (value * 60); }
     }
}

public class ShutdownTime
{
    protected int _sekunden;

    public string HerunterfahrenTimer 
    {
        get { return $"-s -t {_sekunden}"; }
    }
}

There is no possibility now for these to be out of sync; setting the minutes means the seconds are updated and the shutdown argument string will be generated when it is requested

^{note, I've also fixed your code up to regular C# conventions- strive to only use snake case on CONSTANTS_LIKE_THIS, don't prefix public things with "Public" and be consistent with the leading underscores on field names; all or none}