Can't add rectangles into rectangle list [closed]

Question

When i run this code, it gives me "Object reference not set to an instance of an object." here

clickableArea.Add(temp);

here is the entire class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace ScreenManager
{
class Menu
{
    public List<string> MenuItems;
    private List<Vector2> Position;
    private int iterator;
    public string InfoText { get; set; }
    public string Title { get; set; }
    public List<Rectangle> clickableArea;


    public int Iterator
    {
        get
        {
            return iterator;
        }
        set
        {
            iterator = value;
            if (iterator > MenuItems.Count - 1) iterator = MenuItems.Count - 1;
            if (iterator < 0) iterator = 0;
        }
    }

    public Menu()
    {
        Title = "Title";
        MenuItems = new List<string>();
        MenuItems.Add("New Game");
        MenuItems.Add("Options");
        MenuItems.Add("Exit Game");
        Iterator = 0;
        InfoText = string.Empty;
    }



    public int GetNumberOfOptions()
    {
        return MenuItems.Count;
    }

    public string GetItem(int index)
    {
        return MenuItems[index];
    }

    public void DrawMenu(SpriteBatch batch, int screenWidth, SpriteFont arial)
    {
        batch.Begin();

        Vector2 FontOrigin = arial.MeasureString(Title) / 2;

        batch.DrawString(arial, Title, new Vector2(screenWidth / 2 - arial.MeasureString(Title).X / 2, 20), Color.LightGreen, 0, FontOrigin, 1.0f, SpriteEffects.None, 0.5f);

        int yPos = 100;
        for (int i = 0; i < GetNumberOfOptions(); i++)
        {
            Rectangle temp;

            Color colour = Color.White;
            if (i == Iterator)
            {
                colour = Color.Gray;
            }



            batch.DrawString(arial, GetItem(i), new Vector2(screenWidth / 2 - arial.MeasureString(GetItem(i)).X / 2, yPos), colour);

            int reclengthX = (int)arial.MeasureString(MenuItems[i]).X;
            int reclengthY = (int)arial.MeasureString(MenuItems[i]).Y;

            int recposX = (int)(screenWidth / 2 - arial.MeasureString(MenuItems[i]).X / 2);

            temp = new Rectangle(reclengthX, reclengthY, recposX, yPos);

            clickableArea.Add(temp);

            yPos += 50;
        }
        batch.End();
    }

    public void DrawEndScreen(SpriteBatch batch, int screenWidth, SpriteFont arial)
    {
        batch.DrawString(arial, InfoText, new Vector2(screenWidth / 2 - arial.MeasureString(InfoText).X / 2, 300), Color.White);
        string prompt = "Press Enter to Continue";
        batch.DrawString(arial, prompt, new Vector2(screenWidth / 2 - arial.MeasureString(prompt).X / 2, 400), Color.White);
    }

}


}

Answer 1

clickableArea = new List<Rectangle>();

...needs to come first. Your list is not yet instantiated, so you cannot add anything to it. All you have there at the moment is an empty reference.