Valid return value becomes null in receiver in C#

Question

I'm just getting into C#, so forgive me if this is a basic question. I'm building a WPF application using .NET 4.0 and VS 2010.

I have a class in which I'm storing a List of objects; the objects have a Point object as a field. One of the method returns the object in list at a specific location:

public Marker markerAtLocation(Point location) {
    foreach (Marker nextMarker in Markers)
        if (nextMarker.Location().Equals(location))
            return nextMarker;
    return null;
}

Setting breakpoints and using Console.WriteLine I've confirmed that nextMarker is valid at the return. However, in the receiver the object is always null:

Marker top = markerAtLocation(new Point(location.X, location.Y + 1));
if (top == null)
    Console.WriteLine("Top is null");
else
    Console.WriteLine("Top is " + top.ToString());
Marker bottom = markerAtLocation(new Point(location.X, location.Y - 1));
if ((bottom != null) && (bottom.player == otherPlayerType()) && (top != null) && (top.player == otherPlayerType()))
    return true;

I don't know what's going wrong here…

Note that I'd initially thought it was an issue with .NET's Point struct using double values. I know in my app the location values will always be integers so I didn't use the .NET Point and created my own:

class Point {
    public int X, Y;

    public Point(int X, int Y) {
        this.X = X;
        this.Y = Y;
    }

    public bool Equals(Point anotherPoint) {
        return ((anotherPoint.X == X) && (anotherPoint.Y == Y));
    }
}

I'd appreciate any help!

Edit: In response to pbirkoff:

class Grid {
    public List<Marker> Markers;

    public Grid() {
        Markers = new List<Marker>();
    }

    public Grid(List<Marker> markers) {
        this.Markers = markers;
    }

    public void addMarker(Marker newMarker) {
        Markers.Add(newMarker);
    }

I've tried the solutions below to the best of my ability but none of them have helped. I'm including a link to the project itself as well as the problem I'm attempting to solve.

Project: http://dl.dropbox.com/u/7828009/ACSLPetteia.zip
Problem: http://wcipeg.com/etc/ACSL/VOL%2030/ACSL%20Petteia_sr_3.doc

Thanks in advance!

Answer 1

I implemented your code as succinctly as I could, making some mocks where appropriate (code below), and I cannot get it to fail. What am I missing in my code sample:

class Program
{
    static void Main(string[] args)
    {
        LoadMarkers();
        var location = new Point(45, 45);
        Marker top = markerAtLocation(new Point(location.X, location.Y + 1));
        if (top == null)
            Console.WriteLine("Top is null");
        else
            Console.WriteLine("Top is " + top.ToString());
        Marker bottom = markerAtLocation(new Point(location.X, location.Y - 1));

    }
    public static List<Marker> Markers = new List<Marker>();
    private static void LoadMarkers()
    {
        for (var q = 0; q < 50; q++)
            for (var w = 0; w < 50; w++)
                Markers.Add(new Marker(q, w));
    }
    public static Marker markerAtLocation(Point location)
    {
        foreach (Marker nextMarker in Markers)
            if (nextMarker.Location().Equals(location))
                return nextMarker;
        return null;
    }
}
class Marker
{
    private Point _loc;
    public Marker(int x, int y) { _loc = new Point(x, y); }
    public Point Location() { return _loc; }
}
class Point
{
    public int X, Y;
    public Point(int X, int Y)
    {
        this.X = X;
        this.Y = Y;
    }
    public bool Equals(Point anotherPoint)
    {
        return ((anotherPoint.X == X) && (anotherPoint.Y == Y));
    }
}