Class with a List Add to list

scott griffin

Ok that subject was probably not the best in the world but this is what is going on.

I have some code that looks something like this.

public class CLASS
{

public string firstprop {get; set;}

public List secondprop{get; set;}

}

now I could easily add a value to CLASS.firstprop = "mystring";

but when trying to add a value to CLASS.secondprop = "mystring"
it wont work I get a null exception.

I am trying to consume an xml file and fill the class with the data.

of course this is just thrown together code this is not what my code specifically looks like but it is close enough to get a good idea of what may be going wrong.

I am using a XMLReader to cycle through the XML file to get the data and it will get everything except it blows up when it gets to the list part

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes15y ago
Accepted answer
Before adding strings to the list, you first need to check whether the list is null and, if it is, create a new list:

CLASS c = new CLASS();

if (c.secondprop == null)
{
c.secondprop = new List();
}

c.secondprop.Add("mystring");
scott griffin15y ago
Vulpes, I tried that and it worked perfectly. Thank you
Vulpes15y ago
Incidentally, to avoid having to do the null check, you could include a constructor in your class which initializes the list automatically:

public class CLASS
{
public string firstprop {get; set;}

public List secondprop{get; set;}

public CLASS()
{
secondprop = new List();
}
}

You could then just do:

CLASS c = new CLASS();
c.secondprop.Add("mystring");

As long as you don't subsequently set secondprop to null, that will continue to work.
Hemant Kumar15y ago
Hi for your problem you need to do like this
public class CLASS
{

public string firstprop {get; set;}//This is a Property of type String.Here you can set only one value
public List secondprop{get; set;}//Here this is a Property of Collection type String.Here you can set many values of String Type.
}
Please do like this
1. Create a object to that Class
CLASS objClass=new CLASS();
objClass.Add("Hemant");
objClass.Add("Kumar");.
scott griffin15y ago
You know I have looked all around online (probably not searching the correct terms)
I have not been able to find anything that was as clear as what you just suggested. I get off work in 4 hours and when I get home that is the first thing I am going to try.

Thank you so much