Setting values to EMPTY but not NULL by default in C#

Question

I have a Mainclass in my code with various a list and various subset. When I try

main k = new main();
k.main.addressinfo.addressline1 = "XXX";

I am getting the error "Object reference not set to an instance of an object// NULLEXCEPTION."

public class Mainclass
{
    public List<main> mainset { get; set; }
 // do sth to load and save model info
}
 public class main
{
    public personalinfo info { get; set; }
    public addressinfo currentaddr { get; set; }
    public addressinfo[] otheraddr { get; set; }
    public telephone currenttel { get; set; }
    public telephone[] othertel { get; set; }
 }
public class addressinfo
{
    public string Addressline1 { get; set; } 
    public string Addressline2 { get; set; }
    public string City { get; set; }
    public string postcode { get; set; 
}
public class telephone
{
    public int tel { get; set; }
}

Since the Class contains lists and arrays I am a little confused as to how to set the default values of string to EMPTY but not NULL. Also How do I ensure that the Childrens by default have One EMPTY but not NULL Object?

Community · Accepted Answer · 2013-06-29 21:40:17Z

3

You need to initialize your objects

public personalinfo info = new personalinfo();
public addressinfo currentaddr = new addressinfo();
public telephone currenttel = new telephone();

edited Jun 29, 2013 at 21:40

CommunityBot

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answered Jun 29, 2013 at 21:06

mcmonkey4eva

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4 Comments

Flood Gravemind Over a year ago

I know but what about the Arrays? Do I need to initialize them as well?

mcmonkey4eva Over a year ago

Yes, it would help. Like this: public addressinfo[] otheraddr = new addressinfo[2] {new addressinfo(), new addressinfo()}; All classes need to be initialized, structs do not. (EG, int and string are both structs)

Lukazoid Over a year ago

@mcmonkey4eva System.String is a class, not a struct.

mcmonkey4eva Over a year ago

@Lukazoid - ... oh yeah, it is. Woops. Wasn't thinking. Yeah strings need to be initializing too, but it'll let you get away with just public string mystring = ""; instead of new string(); or anything like that.

Jan Dobkowski · Accepted Answer · 2013-06-29 21:15:14Z

0

You have to define constructors for your classes and inside them set the properties to their default values.

answered Jun 29, 2013 at 21:15

Jan Dobkowski

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Comments

Flood Gravemind · Accepted Answer · 2013-06-29 21:41:32Z

0

@Using mcmonkey4eva Answer

public personalinfo info = new personalinfo();
public addressinfo currentaddr = new addressinfo();
public telephone currenttel = new telephone();

public addressinfo[] otheraddr = new addressinfo[1];
public List<main> mainset = new List<main>();

answered Jun 29, 2013 at 21:41

Flood Gravemind

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4 Comments

Tim Over a year ago

If mcmonkey4eva's answer was the one that helped you the most, you should accept the answer.

mcmonkey4eva Over a year ago

What Tim said - also, public addressinfo[] otheraddr = new addressinfo[1]; should probably be public addressinfo[] otheraddr = new addressinfo[1] { new addressinfo(); };, otherwise it will be an array containing only a null.

Flood Gravemind Over a year ago

Didnt not realise that the Correct symbol was to mark as answer :

Flood Gravemind Over a year ago

Changed arrays to list to overcome problems that Tim pointed out.

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