Arrays NullReference Exception

Question

The code is in German but it's not complicated. I'm creating an employee array, and in the end I have to sum all the monthly salaries ("lohnkosten" in german).

The problem I get is the NullReferenceException because I'm trying to have a [10] array and I have initialized only [6] members/employees in it. This is on purpose 'cause I want to have empty "slots" to write a method of adding and removing the members of this array. Now, when it tries to add all the salaries of all the members it comes to a null (empty) "slot" and therefore throws the NullReferenceException.

Is there a way to say to the program something like "if the null spot comes up, ignore it/skip it and do the rest." And I have to say in advance, I can't use List; it would be easier, but unfortunately I can't.

mitarbeiter.Berechnung() is the method for getting an employee's salary based on the hours which are the fourth parameter in the constructor.

Mitarbeiter[] alleMit = new Mitarbeiter[10];
alleMit[0] = new Arbeiter("001689", "Jimmy Page", "Lange Gasse 6, 1060 Wien", 2005, 10.75, 325.90);
alleMit[1] = new Arbeiter("001055", "Michael Jäger", "Lerchenfelderstraße, 1070 Wien", 1998, 12.50, 489.60);
alleMit[2] = new Angestellter("03569", "Toni Montana", "Margaretenstrasse 68, 1040 Wien", 2008, 11.85);
alleMit[3] = new Angestellter("03521", "Ray Charles", "Friedensbrücke 2, 1180 Wien", 2000, 12.65);
alleMit[4] = new Manager("00112", "Sarah Schwack", "Wiedner Haupstrasse 25, 1040 Wien", 2009, 14.75, 624.14);
alleMit[5] = new CEO("001", "Robert Plant", "Am hof 7, 1010 Wien", 1997, 22.50, 1445.80);

double lohnKosten = 0;
foreach (Mitarbeiter mitarbeiter in alleMit)
{
    mitarbeiter.Drucken();
    lohnKosten += mitarbeiter.Berechnung();
}
Console.WriteLine("\nLOHNKOSTEN: " + lohnKosten + " euro");

Alexandre Rondeau · Accepted Answer · 2014-01-15 13:08:30Z

3

You could use LinQ to remove null entries before looping them. Like this

foreach(Mitarbeiter mitarbeiter in alleMit.Where(x => x != null))
{
    mitarbeiter.Drucken();
    lohnKosten += mitarbeiter.Berechnung();
}

edited Jan 15, 2014 at 13:08

answered Jan 15, 2014 at 1:38

Alexandre Rondeau

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Selman Genç · Accepted Answer · 2014-01-15 01:38:30Z

2

Just use an if statement and check for null:

foreach(Mitarbeiter mitarbeiter in alleMit)
{
    if(mitarbeiter != null)
    {
       mitarbeiter.Drucken();
       lohnKosten += mitarbeiter.Berechnung();
    }

}

answered Jan 15, 2014 at 1:38

Selman Genç

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