How can I solve this null reference error?

Question

I have an array where the user can fill it up with objects. Objects are different sodas. There is a function in this simulator where the user has the option to find a specific soda. I don't want it to be case-sensitive so im using the method ToLower(). Everything works fine until one of the spots in the array is empty. I get a null reference error.

I've been trying to solve this issue by using a if statement but then the variable is unavailable in other statements.

How can i solve my issue???

Thanks in advance!

do
{
    name = Console.ReadLine();
    nameL = name.ToLower();

    if (name == "h" || name == "H")
        break;

    for (int i = 0; i < sodas.Length; i++)
    {
        sodasL = sodas[i].Name.ToLower();

        if (name == "h" || name == "H")
        {
            Run();
            break;
        }
        else if (sodas[i] == null)
            Console.WriteLine("Det är tomt på indexet: {0}!", i + 1);//translation: its empty at index..
        else if (sodasL != nameL)
            Console.WriteLine("Drycken hittades inte på indexet: {0}.", i + 1);//translation: Could not find soda at index...
        else if (sodasL == nameL)
        {
            Console.WriteLine("Drycken {0} finns på indexet: {1}.\n", sodas[i].Name, i + 1);//translation: found soda at index...

            Console.WriteLine("Vill du ta bort drycken?");//translation do you want to remove soda?
            Console.WriteLine("[J]a");//yes
            Console.WriteLine("[N]ej");//no
            Console.WriteLine("[G] för nästa {0}.", sodas[i].Name);
            string inmatat = Console.ReadLine();
            if (inmatat == "j" || inmatat == "J")
            {
                amount_bottles--;
                sodas[i] = null;
                Console.WriteLine("Drycken har tagits bort! Sök efter en annan dryck eller [H] för Huvudmenyn");//soda has been removed
                break;
            }
            else if (inmatat == "n" || inmatat == "N")
            {
                Console.WriteLine("Drycken är kvar! Sök efter en annan dryck eller [H] för Huvudmenyn.");//soda has not been removed
                break;
            }
        }
    }
} while (name != "h" || name != "H");

Answer 1

According to your code, you add objects to sodas. Let's say that your object looks like this class:

public class Container
{
    public string Name;
}

When you add a new object without initialisation of the Name field, like:

sodas[0] = new Container();

The field Name is null. So, in this case, when you call sodasL = sodas[i].Name.ToLower(), it looks like:

string name = sodas[0].Name; // name = null!!!
sodasL = name.ToLower(); // You try to call the method of an object, but the reference is null.

Here is a couple of solutions:

1. You need to init Name by default (it may be an empty string).

public class Container
{
    public string Name = "";
}

2. You may check Name before the ToLower call.

string name = sodas[i].Name;
if (name != null)
{
    sodasL = name.ToLower();
    // ...
}