Question

I’m learning about generics, so I’m trying to make my own generic array class, which I can use to make an array of strings or an array of numeric data. This generic class has some different methods, forExample, I can add data and remove data, and search for data. All these methods works like a charm with numeric data, but I’m having some problems with making it work with strings, since it’s a reference type and the default value is null, which makes my methods throw null exceptions.

My Class looks like this:

class MyArray<T> : IComparable<T>, IEnumerable<T>, IEnumerator<T>
{
    T[] data = new T[10];

    private int currentIndex = 0;

    //This method works as intended, both with strings and ints
    public void Add(T Value)
    {
        data[currentIndex] = Value;
        currentIndex++;
        if (currentIndex == data.Length)
        {
            T[] tmp = new T[data.Length + 10];
            data.CopyTo(tmp, 0);
            data = tmp;

        }
    }
    //Can't figure out how to make this method work with strings
    public void RemoveItem(T Value)
    {
        T[] tmp = new T[data.Length - 1];
        int i = 0;
        foreach (T ele in data)
        {
            if (!ele.Equals(Value))//This line gives me a nullRefException when I'm using strings
            {
                tmp[i] = ele;
                i++;
            }

        }
        data = tmp;   
    }

My Main form where I’m adding the data and trying to remove it looks like this:

    static void Main(string[] args)
    {
        MyArray<string> StringArray = new MyArray<string>();

        StringArray.Add("1");
        StringArray.Add("2");
        StringArray.RemoveItem("2");
    }

I can’t figure out a clever way to remove the data again, when it’s a string, because of the default value of null.

Thanks in advance 🙂

Answer 1

Rather than ele.Equals(Value), use EqualityComparer<T>.Default.Equals(ele, Value); this will work correctly with null (for reference-types), Nullable<T> (for value-types), types that implement IEquatable<T>, and any other types using object.Equals.

You might want to cache it, though:

var comparer = EqualityComparer<T>.Default;
//loop
   if(comparer.Equals(ele,Value)) {...}