Thread: Arrays as fields

You are exposing your internals to the public, you won't get a notification if a value changes.

Code:

using System;
using System.Drawing;

namespace ConsoleApplication1
{
    internal class Test
    {
        private PointF[] inputArray;

        public PointF[] InputArray
        {
            get
            {
                Console.WriteLine(" G etter called");

                return inputArray;
            }
            set
            {
                Console.WriteLine(" S etter called");

                inputArray = value;
            }
        }
    }

    internal class Program
    {
        static void Main()
        {
            Test MyObjectInstance = new Test();

            Console.WriteLine( "Calling Setter:");

            // this will call the setter. A new array gets set.
            MyObjectInstance.InputArray = new PointF[100];

            Console.WriteLine("Calling Getter:");
            // 
            // the following line will call the -> getter <-. The array is taken and one value of it is changed.
            // Not the array itself is changed, it's still at the same position.
            //
            // PointF[] array = MyObjectInstance.InputArray;
            // array[50] = new PointF(100f, 200f);
            //
            // would have the same effect
            //
            MyObjectInstance.InputArray[50] = new PointF(100f, 200f);

            Console.ReadLine();
        }
    }
}

Consider another design, the easiest way would be a setter function, maybe accompanied by a getter function returning a readonly ICollection of some sort.

You need a class that wraps the array assignment, so you can perform whatever actions you want on the assigned data (in your case a translation). Notice the self-indexer in PointList ( "this[int Index]" ), this is what gives the illusion of indexing the array while in fact you're indexing the class (see code at bottom).

Code:

	public class PointList
	{
		public PointList(System.Drawing.PointF[] Points, System.Drawing.PointF[] TranslatedPoints)
		{
			_Points = Points;
			_TranslatedPoints = TranslatedPoints;
		}

		public System.Drawing.PointF this[int Index]
		{
			get
			{
				return _Points[Index]; //Retrieve the original point
			}
			set
			{
				_Points[Index] = value; //Store the original point
				_TranslatedPoints[Index] = TranslatePoint(value); //Store the translated point
			}
		}

		private System.Drawing.PointF TranslatePoint(System.Drawing.PointF Point)
		{
			//*** Translate somehow ***

			return Point;
		}

		private System.Drawing.PointF[] _Points;
		private System.Drawing.PointF[] _TranslatedPoints;
	}

	public class SomeClass
	{
		public SomeClass()
		{
			//Not sure if it's your intention to store both original and translated points,
			//but if so you need two arrays
			_Points = new System.Drawing.PointF[666];
			_TranslatedPoints = new System.Drawing.PointF[666];

			_InputArray = new PointList(_Points, _TranslatedPoints);
		}

		public PointList InputArray
		{
			get
			{
				//Expose the PointList class
				return _InputArray;
			}
		}

		private System.Drawing.PointF[] _Points = null;
		private System.Drawing.PointF[] _TranslatedPoints = null;

		private PointList _InputArray = null;
	}

Then you can use it like so:

Code:

var c = new SomeClass();
c.InputArray[23] = new System.Drawing.PointF(12.34f, 56.78f);