Sort point3dcollection by x

[kresimir.kukec]

I want to sort point3dcollection by x value. How I do that?

[norman.yuan · Accepted solution]

Since Point3dCollection is an IList and IEnumerable, you can sorted easily with System.Linq namespace methods. Here is an example:

[CommandMethod("SortPt")]
public static void SortPoints()
{
    Document dwg = CadApp.DocumentManager.MdiActiveDocument;
    Editor ed = dwg.Editor;

    Point3d[] pts = new Point3d[]
    {
        new Point3d(10.0,2.0,0.0),
        new Point3d(8.0,2.0,0.0),
        new Point3d(6.0,2.0,0.0),
        new Point3d(4.0,2.0,0.0),
        new Point3d(2.0,2.0,0.0),
        new Point3d(0.0,2.0,0.0),
    };

    Point3dCollection col = new Point3dCollection(pts);
    IEnumerable<Point3d> sorted = SortPoint3dCollection(col);

    foreach (var p in sorted)
    {
        ed.WriteMessage("\nPoint.X={0}", p.X);
    }

    Autodesk.AutoCAD.Internal.Utils.PostCommandPrompt();
}

private static IEnumerable<Point3d> SortPoint3dCollection(Point3dCollection points)
{
    var pt = from Point3d p in points orderby p.X ascending select p;
    return pt;
}

[khoa.ho · Accepted solution]

Using LINQ for IEnumerable type class is great. This code will work the same:

point3dCollection.Cast<Point3d>().OrderBy(point => point.X);

[_gile]

Hi,

Another way, if the points are stored in a List<Point3d> structure:

pointList.Sort((p1,p2) => p1.X.CompareTo(p2.X));

[khoa.ho]

Agree. This is an implementation of your code using Array as an alternative to List.

public static Point3dCollection Sort(this Point3dCollection collection, bool descending = false)
{
    Point3d[] points = collection.Cast<Point3d>().ToArray<Point3d>();
    Array.Sort<Point3d>(points,
        delegate(Point3d point1, Point3d point2)
        {
            if (descending)
            {
                return point2.X.CompareTo(point1.X); // point2.X - point1.X
            }
            else
            {
                return point1.X.CompareTo(point2.X); // point1.X - point2.X
            }
        });
    return new Point3dCollection(points);
}

[BKSpurgeon]

Hi just a little confused:

will the original point3dCollection be reordered or will one have to create a new ordered list.

e.g. 

Do I have to do this:

Point3dCollection newOrderedList = point3dCollectionOldList.Cast<Point3d>().OrderBy(point => point.X);

EDIT: actually the above does not work It says that one cannot convert type system.linq.iOrderedEnumerable<autodesk.autocad.Geometry.Point3d> to <AutoDesk.Autocad.Geometry.Point3dCollection> any ideas on how to simply create a new list?

or will just doing this suffice to reorder the list:

point3dCollection.Cast<Point3d>().OrderBy(point => point.X);

rgds

BK

[_gile]

Hi,

Most Linq extension methods (as Cast and OrderBy) return an IEnumerable<T> lazy sequence.

If you need a classic collection as Point3d[] or List<Point3d> you'l have to convert the IEnumerable<Point3d> with the ToArray or ToList extension methods.

If you need a Point3dCollection, you can use the Point3dCollection constructor which requires an Point3d array as parameter.

try this way:

Point3dCollection newOrderedList = new Point3dCollection(
    OldList
    .Cast<Point3d>()
    .OrderBy(point => point.X)
    .ToArray());