Question

I have one list with points. I am applying:

var result = neighbors.SelectMany(element => GenerateNeighbors(element)).Distinct<Point3D>().ToList<Point3D>();

To generate all neighbors from each point of this list. But I have another list with other points, and this neighbor-generation can generate points already add to that one.

How to I remove from result list the repeated elements from the other list? Any linq function with some predicate I can use to improve this?

Thanks a lot!

EDIT
New code:

    class Point3D : IEquatable<Point3D>
    {
        public int X { get; set; }
        public int Y { get; set; }
        public int Z { get; set; }
        public bool visited { get; set; }
        public int life { get; set; }

        public Point3D(int _x, int _y, int _z)
        {
            this.X = _x;
            this.Y = _y;
            this.Z = _z;
            this.visited = false;
            this.life = 2;
        }

        public int GetHashCode(Point3D obj)
        {
            throw new NotImplementedException();
        }

        public override Boolean Equals(object o)
        {
            if (!(o is Point3D)) return false;
            return Equals((Point3D)o);
        }

        public Boolean Equals(Point3D p)
        {
            return Equals(this, p);
        }

        public static Boolean Equals(Point3D a, Point3D b)
        {
            return a.X == b.X && a.Y == b.Y && a.Z == b.Z;
        }
    }

Answer 1

You can use the Linq Except() extension method:

result = result.Except(otherList).ToList();

Your Point3D class should provide an appropriate implementation of Equals / GetHashCode (yes, you do have to implement it, throwing a NotImplementedException won’t work) or implement (more explicit) IEquatable<Point3D> for this to work, or alternatively you can pass a custom IEqualityComparer as second parameter to Except()