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Custom auto properties in C# [duplicate]

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C# 3.0 Auto-Properties - Is it possible to add custom behaviour?
(6 answers)
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I have the following class with auto properties:
class Coordinates
{
public Coordinates(int x, int y)
{
X = x * 10;
Y = y * 10;
}
public int X { get; set; }
public int Y { get; set; }
}
As you can see from the constructor I need the value to be multiplied by 10.
Is there anyway to do it without removing autoproperties?
I tried the following not thinking that it causes recursion and then everything goes fubar
public int X { get {return X;} set{ X *= 10;} }
I would like to assign values to X and Y multiplied by 10.
Coordinates coords = new Coordinates(5, 6); // coords.X = 50 coords.Y = 60
coords.X = 7; // this gives 7 to X but I would like it to be 70.

In order to make setter working like that, you'll need to use backing field:
class Coordinates
{
public Coordinates(int x, int y)
{
X = x;
Y = y;
}
private int _x;
public int X
{
get { return _x; }
set { _x = value * 10; }
}
private int _y;
public int Y
{
get { return _y; }
set { _y = value * 10; }
}
}
Given your example:
Coordinates coords = new Coordinates(5, 6); // coords.X = 50 coords.Y = 60
coords.X = 7; // this gives 70
However, I don't recommend you having such setter because it could lead to confusion. It's better to have a dedicated method which will do such multiplication. In the end, your code will be more descriptive and intuitive.

You get a recursion, because you again call the same property, which in turn calls the same property, which in turn calls the same property... you get the point.
public int X { get {return X;} set{ X *= 10;} }
How does auto properties works ?
Behind the scenes Properties are actually methods, which means they don't actually store data. So who saves the data ? AutoProperties generate private backend field to save the data.
So in the simple declaration of auto property
int X { get; set; }
The compiler translate it into something like that
private int <X>k__BackingField;
public int X
{
[CompilerGenerated]
get
{
return <X>k__BackingField;
}
[CompilerGenerated]
set
{
<X>k__BackingField = value;
}
}
So no matter if you use it as Auto Properties or simple property, they are the same.
Now, to answer you question, with paraphrasing, "How do i return the value multiply with 10"
You can solve it with using 2 ways:
1. By saving the data multiply by 10 (setter implementation)
2. By returning the data multiply by 10 (getter implementation)
I won't elavorate, which one you should use, because for this kind of simple scenario, both will be perfectly valid.
I would just say that some of the factors for the choice will be micro(micro micro micro) performence, true state storage.
Here is the setter implementation
private int _x;
public int X
{
get
{
return _x;
}
set
{
return _x*10;
}
}

NUnit Test For Setting Position C#

So I'm creating a Snake-game and want to test that the "Snake-food" changes Position when "eaten".
So I have a simple Position-class that looks kinda like this:
public class Position
{
public int XCoordinate {get; set;}
public int YCoordinate {get; set;}
public Position(int x, int y)
{
XCoordinate = x;
YCoordinate = y;
}
}
And in the test, I want to see that the Position of the food updates when eaten. Because there seems to be no good way of comparing objects, I'm doing this with Assert like this(simplified method):
[Test]
public void AssertFoodSpawnsOnNewLocationWhenEaten()
{
int expectedX = _sut.Food.Pos.XCoordinate;
int expectedY = _sut.Food.Pos.YCoordinate;
_sut.FeedSnake();
int resultX = _sut.Food.Pos.XCoordinate;
int resultY = _sut.Food.Pos.YCoordinate;
Assert.AreNotEqual(expectedX, resultX);
Assert.AreNotEqual(expectedY, resultY);
}
Realized that my solution is a bad one, since the Food-Position could have been updated even tough e.g. expectedX and resultXare equal.
Does anyone have a tip how I could test this? Can you do some kind of Assert.AreNotEqual checking if both x-and y-coordinates are not equal?
Thankful for any help!

Made a separate private function that determines if the x and y coordinates are the same. This checks if _sut.FeedSnake()updates the Food-position when eaten.
[Test]
public void AssertFoodSpawnsOnNewLocationWhenEaten()
{
Position expected = _sut.Food.Pos;
_sut.FeedSnake();
Position result = _sut.Food.Pos;
Assert.False(IsPositionEqual(expected, result));
}
private bool IsPositionEqual(Position Pos1, Position Pos2)
{
if (Pos1.XCoordinate == Pos2.XCoordinate &&
Pos1.YCoordinate == Pos2.YCoordinate)
{
return true;
}
return false;
}

How can I search a List for a partial match of variables inside its listed elements, then return one variable from a found match?

I have a custom list that contains custom classes that each contain 3 integer variables (x, y, height). I want to be able to search the listed elements for any that match both 'x,y' and then return 'height' in the instance I don't know what 'height' currently is, only the current x/y.
This is the custom class
public class ConstructionCoordinates
public int x;
public int y;
public int height;
public ConstructionCoordinates(int xCoord, int yCoord, int levelHeight)
{
x = xCoord;
y = yCoord;
height = levelHeight;
}
This is the Custom List
public List<ConstructionCoordinates> constructionCoordList = new List<ConstructionCoordinates>();

foreach (ConstructionCoordinates constructionCoord in constructionCoordList) {
if (constructionCoord.x == x && constructionCoord.y == y) {
// Place your logic here
}
}

C# constructors with parameters - passing on

I got a question about constructors for my Windows Forms Application. First of all I want to say that I am new to programming.
The thing is this. I am making a constructor in another class that should hold different parameter values. In this case it should be int X, int Y, int Length, int Height. What I want to do here is to make the X, Y, Length and Height all random for my picturebox. I send code down below:
class Rechthoekcs
{
Random random = new Random();
public int Xas
{
get;
set;
}
public int Yas
{
get;
set;
}
public int Lengte
{
get;
set;
}
public int Breedte
{
get;
set;
}
public Rechthoekcs(int x, int y, int lengte, int breedte)
{
this.Xas = x;
this.Yas = y;
this.Lengte = lengte;
this.Breedte = breedte;
x = random.Next(x);
y = random.Next(y);
lengte = random.Next(lengte);
breedte = random.Next(breedte);
}
From my Form1 I want to call this class/constructor
But it gives me an error. It says "Does not contain a constructor with 0 arguments" and I know that because I typed the x, y, length and width. But I cannot add just the variables from the other class into the new parameter. I really don't get it. I find constructors very hard. I never know what parameters I should give with it...
I send the code down below from my Form1:
public partial class Form1 : Form
{
Rechthoekcs Rechthoek = new Rechthoekcs(.......);
public Form1()
{
InitializeComponent();
}
It it really frustrating for me. I tried looking up on the web and books and such but all the explanation about which parameters should be given for a constructor is not clear to me. Could someone explain this? Not understanding it drives me insane. Plus I am getting often stuck at these points..

public Rechthoekcs(int x, int y, int lengte, int breedte)
{
this.Xas = x;
this.Yas = y;
this.Lengte = lengte;
this.Breedte = breedte;
x = random.Next(x);
y = random.Next(y);
lengte = random.Next(lengte);
breedte = random.Next(breedte);
}
You are assigning the values of the parameters to your private Data Members before you do anything "randomizing" about them. You are simply changing the values of the parameters in your constructor without assigning them. Swap the order you do them in.
public Rechthoekcs(int x, int y, int lengte, int breedte)
{
x = random.Next(x);
y = random.Next(y);
lengte = random.Next(lengte);
breedte = random.Next(breedte);
this.Xas = x;
this.Yas = y;
this.Lengte = lengte;
this.Breedte = breedte;
}
Now you have successfully randomized your values that will be set to your data member variables ASSUMING that those variable you put in there actually exist, which they should. Better/more modular code would do this randomization where you create your object.
Ex: Object foo = new Object(new Random, new Random, new Random, new Random)

Not the answer OP is looking for, but this is how you solve "I don't yet know the value but I need to construct object anyway" version of the question.
You can delay requesting the data by passing Func<T> for each parameter instead of just T assuming the values actually will be available by the time they needed:
class UseDelayedValues
{
Func<int> x;
public UseDelayedValues(Func<int> x)
{
this.x = x;
}
public UseWithX(int other)
{
return other + x();
}
}
int value = 0;
var r = new UseDelayedValues(() => value);
value = 42;// get some value
Console.WriteLine(r.UseDelayedValues(1));
var delayedFromTextbox = new UseDelayedValues(() => int.Parse(textBox1.Value));
Lines using the UseDelayedValues can be spread over time. I.e. instance constructed in constructor, but value used only when form is shown by button click.

how can i get an access to the elements of array in the class

I have a problem which I don't know how to solve. I have a class. This class has two arrays. I would like to get access via properties. How can I do it? I tried to use indexers, but it is possible if I have only one array. Here what I want to do:
public class pointCollection
{
string[] myX;
double[] myY;
int maxArray;
int i;
public pointCollection(int maxArray)
{
this.maxArray = maxArray;
this.myX = new string[maxArray];
this.myY = new double[maxArray];
}
public string X //It is just simple variable
{
set { this.myX[i] = value; }
get { return this.myX[i]; }
}
public double Y //it's too
{
set { this.myY[i] = value; }
get { return this.myY[i]; }
}
}
With this code, my X and Y are only simple variables, but not arrays.
If I use indexers, I get access only to one array:
public string this[int i]
{
set { this.myX[i] = value; }
get { return this.myX[i]; }
}
But how can I get access to second array?
Or I can't use property in this case? And I need only use:
public string[] myX;
public double[] myY;

An example with Tuples.
public class pointCollection
{
Tuple<String,Double>[] myPoints;
int maxArray;
int i;
public pointCollection(int maxArray)
{
this.maxArray = maxArray;
this.myPoints = new Tuple<String,Double>[maxArray];
}
public Tuple<String,Double> this[int i]
{
set { this.myPoints[i] = value; }
get { return this.myPoints[i]; }
}
}
And to access the points you do...
pointCollection pc = new pointCollection(10);
// add some data
String x = pc[4].Item1; // the first entry in a tuple is accessed via the Item1 property
Double y = pc[4].Item2; // the second entry in a tuple is accessed via the Item2 property

If I got it right, you need some kind or read/write-only wrapper for arrays to be exposed as properties.
public class ReadWriteOnlyArray<T>{
private T[] _array;
public ReadWriteOnlyArray(T[] array){
this._array = array;
}
public T this[int i]{
get { return _array[i]; }
set { _array[i] = value; }
}
}
public class pointCollection
{
string[] myX;
double[] myY;
int maxArray;
public ReadWriteOnlyArray<string> X {get; private set;}
public ReadWriteOnlyArray<double> Y {get; private set;}
public pointCollection(int maxArray)
{
this.maxArray = maxArray;
this.myX = new string[maxArray];
this.myY = new double[maxArray];
X = new ReadWriteOnlyArray<string>(myX);
Y = new ReadWriteOnlyArray<double>(myY);
}
}
and usage
var c = new pointCollection(100);
c.X[10] = "hello world";
c.Y[20] = c.Y[30] + c.Y[40];

The closest you'll come without either changing your data structure or moving to methods is to make a property that returns each array, much like you did in your first code block, except without the [i].
Then, you do var x = instanceOfPointCollection.MyX[someI]; for example.