c# use a class object as a key in dictionary

Question

I have a class that looks like this.

public class Point : IEquatable<Point>
{
    public int _xValue {get;set;}
    public double _yValue {get;set;}

    public Point(int x, double y)
    {
        _xValue = x;
        _yValue = y;
    }

    public override bool Equals(object obj)
    {
        return Equals(obj as Point);
    }

    public bool Equals(Point obj)
    {
        return obj != null && obj._xValue == this._xValue && obj._yValue == this._yValue;
    }


}

I have to implement the GetHashCode function so that I can use it as a dictionary key. But I'm not clear on what the GetHashCode function has to return in this situation. Can someone help me out?

Answer 1

It should return an integer, preferably unique for each seperate instance of the object. A hash value is basically a single number created out of the contents of an object, used to uniquely identify that object. The number one rule is that if two of those Points evaluate as equal to each other, the hash value should be the same for both of them.

A more detailed description is available at MSDN

Answer 2

The GetHashCode function needs to return am integer that will uniquely identify one instance of the object from another so as to avoid collisions when it is used as a key in the dictionary.

You should be able to reliably reproduce the hash code so try and avoid using random or date values as seeds for the hash code.

Answer 3

You could do _xValue ^ _yValue.GetHashCode()