Question

I am having problem with List Object values. Object is an object of class which holding two integer number.

like

List<Object> container;
container.Add(new Coordinates(x_axis, y_axis));  // x_axis=200, y_axis=300

I have to add unique coordinates each time, means next time x_axis, y_axis can never be added to list if it is 200, 300 respectively.

How can I check the already exist item in list objects?

Thanks

Answer 1

Override Equals and GetHashCode for your Coordinates class:

public class Coordinates
{
    public Coordinates(int x, int y)
    {
        X = x;
        Y = y;
    }

    public int X { get; private set; }
    public int Y { get; private set; }

    public override bool Equals(object obj)
    {
        if (!(obj is Coordinates))
        {
            return false;
        }
        Coordinates coordinates = (Coordinates)obj;
        return ((coordinates.X == this.X) && (coordinates.Y == this.Y));
    }

    public override int GetHashCode()
    {
        return (X ^ Y);
    }
}

And use generic List or HashSet of your Coordinates objects:

List<Coordinates> container = new List<Coordinates>();
Coordinates coordinates = new Coordinates(x_axis, y_axis);

if (!container.Contains(coordinates)
    container.Add(coordinates);

And with HashSet:

HashSet<Coordinates> container = new HashSet<Coordinates>();
container.Add(new Coordinates(x_axis, y_axis));