Instantiate string[] field

Question

I'm working on a console application which also had reference to class library. In class library i have following code.

namespace SomeClass  
{  
    public class ClassOne  
    {  
        public string[] SupportedFiles;  
    }  
}

And in console app, program.cs, i'm trying to assign SupportedFiles.

class Program  
    {  
        public ClassOne class1 { get; set; }  
        public Program()  
        {  
            class1.SupportedFiles = new string[] { "Test", "Test" };
           //class1.SupportedFiles[0] = "First";
           //class1.SupportedFiles[1] = "Second"; 
        }  
    }

But the line class1.SupportedFiles = new string[] { "Test", "Test" }; throws

System.NullReferenceException: 'Object reference not set to an instance of an object.'

What am i missing? Am I so dumb instantiating a string array. Please help me out.

You have defined `SupportedFiles` and accessing `SupportedArchitectures` — sujith karivelil, May 11 '18 at 05:36
Possible duplicate of [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — SᴇM, May 11 '18 at 05:50
This question has been asked for numerous times and [duplicated] for numerous time — Prasad Telkikar, May 11 '18 at 05:53

Prasad Telkikar · Answer 1 · 2018-05-11T05:38:17.050

You are missing instance of class where string[] is present

Try with this before accessing string[]

ClassOne cOne = new ClassOne();

Do not miss adding reference of your class library to project where you want to access this string and also include namespace in program.cs file

This can be your working solution:

using SomeClass;
class Program  
    {  
        //Not required to create property of ClassOne
        //public ClassOne class1 { get; set; }  
        public Program()  
        {  
           //In this way, you can create instance of class.
           ClassOne class1 = new ClassOne();
           //Now with the help of instance of class, you can access all public properties of that class
            class1.SupportedFiles= new string[] { "Test", "Test" };
           //class1.SupportedFiles[0] = "First";
           //class1.SupportedFiles[1] = "Second"; 
        }  
    }

SᴇM · Answer 2 · 2018-05-11T05:45:39.473

You have to initialize your object before accessing its members. For that you have several(basic) options:

class Program  
{  
    public ClassOne Class1 { get; set; }  
    public Program()  
    {  
        Class1 = new ClassOne();
        Class1.SupportedFiles= new string[] { "Test", "Test" };
    }  
}

or even better:

class Program  
{  
    public ClassOne Class1 { get; set; }  
    public Program()  
    {  
        Class1 = new ClassOne()
        {
            SupportedFiles = new string[] { "Test", "Test" }
        };
       //class1.SupportedFiles[0] = "First";
       //class1.SupportedFiles[1] = "Second"; 
    }  
}

or if you're using C#6 and above, you have such thing as auto-property initializers:

class Program  
{  
    public ClassOne Class1 { get; set; } = new ClassOne();
    public Program()  
    {  
        Class1.SupportedFiles= new string[] { "Test", "Test" };
       //class1.SupportedFiles[0] = "First";
       //class1.SupportedFiles[1] = "Second"; 
    }  
}

Still ClassOne doesn't have the property `SupportedArchitectures` see updates in the question..! lol — sujith karivelil, May 11 '18 at 05:43

Instantiate string[] field

2 Answers2