C#: Getter and setter expression for array property

Question

How can I write the getter and setter expression for array property CoolerFanIsOn in the class CoolerSystem? I showed the similar desired expression for non-array property IsOn of Lamp class.

class CoolerFan{

    bool isOn;
    public bool IsOn {
        get => isOn;
        set {
            isOn = value;
        }
    }
}

class CoolerSystem {

    private CoolerFan[] = new CoolerFan[5];
    private bool[] coolerFanIsOn = new Boolean[5];

    // invalid code from now

    public bool[] CoolerFanIsOn {
        get => coolerFanIsOn[number];
        set {
            coolerFanIsOn[number] = value;
        }
    }
}

Answer 1

You can use indexer:

public class CoolerSystem
{
    private bool[] _coolerFanIsOn = new Boolean[5];

    public bool this[int index]
    {
        get => _coolerFanIsOn[index];
        set => _coolerFanIsOn[index] = value;
    }
}

Btw, the => are expression bodied properties which were new in C#6. If you can't use (setter was new in C#7) use the old syntax, indexers have nothing to do with it(C#3):

public bool this[int index]
{
    get { return _coolerFanIsOn[index];  }
    set { _coolerFanIsOn[index] = value; }
}

Answer 2

You can write an indexer for your class

public bool this[int index]{
   get { return coolerFanIsOn[index]; }
   set { coolerFanIsOn[index] = value;}
}