We Keep Coding

Only allow certain classes to edit certain properties

I have a class with a PictureBox created as followed:
public class Tile
{
public PictureBox tilePB = new PictureBox(); //properties don't matter in this case
}
I also have a class GameManager. This is like a referee.
I want to make it so the BackColor of Tile.tilePB can only be edited by Gamemanager and nothing else, and no other class.
I currently have a public PictureBox for Gamemanager (to edit) and a public get function for other classes, but I want to actually make this a valid system instead of what I have right now.
Is this even possible? Please include explenation for the required code.
EDIT: I ran into an issue that I hadn't thought off: class Gamemanager is a static class. I do everything in that class via public static functions. Is this still possible? Since this doesn't work.

You can't do this at compile time, but it can be done at runtime:
public class PictureBox
{
private Color _backColor;
public void SetBackColor(Color color)
{
//getting class type that called this method
var stackTrace = new StackTrace();
var stackFrames = stackTrace.GetFrames();
var callingFrame = stackFrames[1];
var method = callingFrame.GetMethod();
//checking if the class type is GameManager
if (!method.DeclaringType.IsAssignableFrom(typeof(GameManager)))
{
throw new FieldAccessException("Only GameManager can set the background color of a PictureBox!");
}
_backColor = color;
}
public Color BackColor => _backColor;
}
public class Tile
{
public PictureBox tilePB { get; set; }
}
//example GameManager class
public class GameManager
{
public void SetBackground()
{
var someTile = new Tile()
{
tilePB = new PictureBox()
};
var someColor = new Color();
someTile.tilePB.SetBackColor(someColor);
}
}
//example class that may want to set picturebox background color
public class MaliciousClass
{
public void SetBackground()
{
var someTile = new Tile()
{
tilePB = new PictureBox()
};
var someColor = new Color();
someTile.tilePB.SetBackColor(someColor);
}
}
Then somewhere:
var gm = new GameManager();
var mc = new MaliciousClass();
gm.SetBackground(); //this is fine
mc.SetBackground(); //this will throw an exception
If you don't want to throw an exception or you want to do something different when "not authorized" class is trying to access the SetBackColor method then just replace throw new FieldAccessException() with return or whatever you want.
Bare in mind the approach presented here is inefficent and it just presents that in can be done at runtime and nothing more than that.

Not sure if this is exactly what you are looking for, but I made this quick test and it seems to be able to differentiate the calling class:
class Program
{
static void Main(string[] args)
{
Type1 something1 = new Type1();
Type2 something2 = new Type2();
something1.runTest();
something2.runTest();
Console.ReadKey();
}
public class Type1
{
public void runTest()
{
Testing.edit(this);
}
}
public class Type2
{
public void runTest()
{
Testing.edit(this);
}
}
public static class Testing
{
public static void edit(object obj)
{
// This is where you test the calling class to make sure
// it is allowed to edit.
Console.WriteLine(obj.GetType().ToString());
}
}
}

The only way I can think of where you enforce this at compile time, end up being a bit complicated. I don't think you'll want to do this.
You can create an interface with properties/methods for everything that only the GameManager is allowed to do. You can implement this interface in a private inner class below Tile, and make sure the only way this object is created is by passing in a GameManager that receives it. Now, the only way the access can 'leak' is if the GameManager 'gives away' the object.
public class GameManager {
public void AddTile(Tile t, Tile.IManagerHook m) {
m.SomeProperty = "set from manager";
}
}
public class Tile
{
public object SomeProperty { get; private set; }
public Tile(GameManager manager) {
manager.AddTile(this, new ManagerHook(this));
}
public interface IManagerHook {
object SomeProperty {get; set;}
}
private class ManagerHook : IManagerHook {
private Tile _tile;
public ManagerHook(Tile t) {
_tile = t;
}
public object SomeProperty {
get{ return _tile.SomeProperty;}
set { _tile.SomeProperty = value; }
}
}
}

(seems) Simply not possible
After asking several programmers, the way I have coded everything and what I want seems to be simply impossible without immensely complicated code - to the point you are better off refacturing everything. Since class Gamemanager is a static class, there will be no instances of it so you can not check if the 'object' that called it is of class Gamemanager. this also doesn't work since Gamemanager is, agian, static.

inherited variable of class2 is different from class1 (C#)

I just made a class Shapes and an other 2 classes ('Triangle' & 'Square') which inherit from 'Shapes'.
public class Shapes
{
private int sides;
}
public class Triangle : Shapes
{
public void init()
{
int sides = 3;
throw new System.NotImplementedException();
}
}
public class Square : Shapes
{
public void init()
{
int sides = 4;
throw new System.NotImplementedException();
}
}
Code is designed using Classdiagram
Question: How should I call the class so that it shows how many sides does a shape has?
Thanks

You need a protected member sides which is used within the init-section of every shape:
public class Shapes
{
protected readonly int sides;
public int NumberOfSides { get { return sides; } }
}
public class Triangle : Shapes
{
public Triangle()
{
this.sides = 3;
}
}
public class Square : Shapes
{
public Square()
{
this.sides = 4;
}
}
As Farhad Jabiyev mentioned using constructors is the usual way to initialize a new instance (see my code above)
Now when you call Shape#NumberOfSides you get 3 for Triangle and 4 for Square:
Shape square = new Square();
int number = square.NumberOfSides();

You need to add a property on the class that has an accessor like this
public class Shapes
{
private int sides;
public int NumberOfSides { get { return sides; } }
}
Then you can go mySquare.NumberOfSides

How can I access members of a private abstract to class for read-only purposes in a public class?

I have a private abstract class called TDSeq in which there are some abstract members and non-abstract members. There are 2 derived classes which it gets data from:- private class TDSeqBuy: TDSeq and private class TDSeqSell: TDSeq.
The members from the private abstract class that I am trying to access are private/public bools/doubles/integers.
The data flows from the derived classes through to the private abstract class by protected abstract name {get;}. After which the data is "moved" to the above mentioned private/public bool/doubles/integers.
I would like to access data for read-only purposes from the abstract class to a public class but do not know how to do that. Could someone please help?
private abstract class TDSeq
{
public event SetupCompletedEventHandler SetupCompleted;
protected abstract double TDSTHigh { get; }
protected abstract double TDSTLow { get; }
protected abstract double SetupStopLevel { get; }
public double highesthigh = 0;
public double lowestlow = 0;
public double truerange = 0;
public double setupstoplevel = 0;
// ...
case TDSTStateSetup.Completed:
if( ValidSetup )
{
Print = "ValidExtSetup";
setupCount++;
SetupDrawText();
//Print = NameIndex;
}
else
{
Print = "ExtSetup Finalised";
tdsetupiscompleted = true;
if (tdsetupiscompleted)
{
Print = "tdsetupiscompleted";
}
if (tdsetupdirection == 1)
{
Print = "tdsellsetupiscompleted";
}
if (tdsetupdirection == -1)
{
Print = "tdbuysetupiscompleted";
}
highesthigh = TDSTHigh;
lowestlow = TDSTLow;
truerange = (highesthigh - lowestlow);
setupstoplevel = SetupStopLevel;
stateSetup = TDSTStateSetup.Finished;
}
// ...
}
I'm trying to publicly access the last 5 lines...

You can also use auto properties to acheive the same without using a private field.
e.g.
private abstract class A
{
protected int Number { get; private set; }
}
private class B : A
{
public int GetNumber()
{
return Number;
}
}

Use protected, not private. Also consider composition over inheritance.
Nested classes are not a good idea. It only limits scope. And protected will not save you there.

If you want access to the properties and them only to be read only, store the values in private fields - and give a protected get property to give read only access to the private fields like so:
private abstract class A
{
private int _number = 5;
protected int Number { get { return _number; } }
}
private class B : A
{
public int GetNumber()
{
return Number;
}
}
private class C : A
{
public int GetNumber()
{
return Number;
}
}

If you want to access data via an object of an abstract class A within a method of a separate, public class X, the abstract class has to be visible to X, so it has to be public (or at least internal, when A and X are part of the same assembly):
public class Program
{
static void Main(string[] args)
{
B b = new B();
X.Test(b);
}
// private does not work here if you want to have a parameter of type A in X
public abstract class A
{
private int _number = 5;
public int Number { get { return _number; } }
}
private class B : A
{
}
}
public class X
{
public static void Test(Program.A a)
{
Console.WriteLine(a.Number);
}
}

Top level classes in an assembly can only be public or internal in terms of accessibility, so I'm assuming your private abstract class and it's derived classes are all nested inside some public class, for starters. Correct?
If so, simply access members of the nested private abstract class that are non-abstract and public by first instantiating the private derived classes inside that parent class via say a public property, then simply call the public field from it:
public class TopClass
{
DerivedClass MyDerivedClass;
public int GetDerivedClassPublicField
{
get
{
DerivedClass MyDerivedClass = new DerivedClass();
return DerivedClass.myfield;//here is access to your abstract class field from outside
}
}
// Private classes must be nested
private abstract class AbstractClass
{
public int myfield = 1;
}
private class DerivedClass : AbstractClass
{
... (derived classes inherit the non-abstract field from the abstract parent by default here) ...
}
}
// now call the public top level class property to get the field in the abstract class
TopClass MyTopClass = new TopClass();
int myInt = MyTopClass.GetDerivedClassPublicField;

A field is fixed value for each class,field is not dependent instances ...?

In below example, i defined number field. This field will work as i wanted but it is not enough efficient to provide my expectations.
number value is fixed value for each class,number is not dependent instances and number support polymorphism. How can i do that ? Or is there another solution for not use unneccesary number field for instances ?
abstract class Main
{
public int number;
public virtual void dostuff(){
int x = number;
}
}
class Derived:Main
{
public ovverride void dostuff(){
int x = number;
}
}

You could just make the number a property and initialise is in each class constructor:
abstract class Main
{
public int number{get; private set;}
public void dostuff(){
int x = number;
}
}
class Derived:Main
{
public Derived()
{
number = 5; // Specific value for each derived class
}
public void dostuff(){
int x = number;
}
}
Looks like I got the wrong end of the stick -- you want to be able to set it statically per class type, which has already been answered.

You could make the property static and then add it to each class:
abstract class Main
{
public static int number;
public virtual void dostuff(){
int x = Main.number;
}
}
class Derived : Main
{
public static int number;
public overide void dostuff(){
int x = Derived.number;
}
}
Edit: I am a bit confused by your comments about polymorhism so i have added some more examples.
Main obj = new Derived();
obj.doStuff(); //This will use Derived.number; as doStuff is and overidden virtual method.
However if you do the following:
abstract class Main
{
public static int number;
public void dostuff(){
int x = Main.number;
}
}
class Derived : Main
{
public static int number;
public new void dostuff(){
int x = Derived.number;
}
}
Then you get different behaviour as below:
Main obj = new Derived();
obj.doStuff() // Will use Main.number
Derived obj2 = (Derived)obj;
obj2.doStuff() // Will use Derived.number
If you want some other kind of behaviour i havn't defined here please exaplin because i do not understand what you want.

friendly classes in c#

actually i refactor some portion of code.
what i want to do is to initialize an object "Task" with an object "TaskArgument".
let s say "TaskArgument" is abstract and "Task" implements a method "OnEnterTask(TaskArgument args)" and is sealed (for some special behavior of the existing system, which is out of scope).
old code:
public sealed class Task : SomeSystemBaseTask {
private int accessMe;
private int meToo;
public void OnEnterTask(TaskArgument args) {
if (args is SimpleTaskArgument) {
accessMe = ((SimpleTaskArgument)args).uGotIt;
meeToo = 0;
} else if (args is ComplexTaskArgument) {
accessMe = ((ComplexTaskArgument)args).uGotItValue * ((ComplexTaskArgument)args).multiplier;
meToo = ((ComplexTaskArgument)args).multiplier - 1;
}
}
}
what would be the best practise avoid the typecheck?
my first stupud thought was:
public abstract class TaskArgument {
internal public abstract Initialize(Task args);
}
public class SimpleTaskArgument : TaskArgument {
public int uGotIt = 10;
internal public Initialize(Task task){
task.accessMe = uGotIt;
}
}
public class ComplexTaskArgument : TaskArgument {
public int uGotItValue = 10;
public int multiplier = 10;
internal public Initialize(Task task){
task.accessMe = uGotItValue*multiplier;
task.meToo = multiplier - 1;
}
}
public sealed class Task : SomeSystemBaseTask {
public int accessMe;
public int meToo;
public void OnEnterTask(TaskArgument args){
args.Initialize(this);
}
}
but then my "accessMe" is public and the "Initialize" method works only with "Task".
so i moved the typechecking to another place (in future).
is there any best practise or good design idea.
..."internal public"... mmhhmm?
another crazy idea was an inner class, but i dont like those and it make such a simple case more complex or don't:
public abstract class TaskArgument {
internal public abstract Initialize(ITaskWrapper wrapper);
}
public class SimpleTaskArgument : TaskArgument {
...
}
public class ComplexTaskArgument : TaskArgument {
...
}
public interface ITaskWrapper {
public int AccessIt { set; get; }
...
}
public sealed class Task : SomeSystemBaseTask {
private int accessMe;
...
class TaskWrapper : ITaskWrapper {
...
}
public void OnEnterTask(TaskArgument args){
args.Initialize(new TaskWrapper(this));
}
}
where is the best place for initialization when it is based on the given Type of the "TaskArgument"?
kindly excuse my bad english knowledge
greetings
mo

Use an interface.
public void OnEnterTask(TaskArgument args) {
if (args is SimpleTaskArgument) {
accessMe = ((SimpleTaskArgument)args).uGotIt;
} else if (args is ComplexTaskArgument) {
accessMe = ((ComplexTaskArgument)args).uGotItValue * ((ComplexTaskArgument)args).multiplier;
}
}
becomes
public void OnEnterTask(ITaskArgument args) {
accessMe = args.GetAccessMe();
}
Then you have your classes implement ITaskArgument and implement the method for each class. In general, when you're doing something like this:
accessMe = ((ComplexTaskArgument)args).uGotItValue * ((ComplexTaskArgument)args).multiplier;
where you're accessing multiple properties on an object to perform a calculation, it usually makes sense to push that logic into the class itself.

Sounds like you want to put the logic associated with each sub-class of TaskArgument onto that class. You could add an abstract method to TaskArgument called Calculate that has the sub-class specific calculation. That would remove the need for your if statements completely:
public class Task {
private int accessMe;
public void OnEnterTask(TaskArgument args)
{
accessMe = args.Calculate();
}
}
You would then put the multiplication or whatever is appropriate into each sub-class.

I would create a public interface, which only exposes the Intialize method. Do your calculations in your derived classes e.g.
public interface ITaskArgument
{
void Initialize(Task task);
}
public abstract class TaskArgument : ITaskArgument
{
protected int _value;
public class TaskArgument(int value)
{
_value = value;
}
public abstract void Initialize(Task task);
}
public class SimpleTaskArgument : TaskArgument, ITaskArgument
{
public SimpleTaskArgument(int value)
: base (value)
{
}
public override void Initialize(Task task)
{
task.AccessMe = _value;
}
}
public class ComplexTaskArgument : TaskArgument, ITaskArgument
{
private int _multiplier;
public ComplexTaskArgument(int value, int multiplier)
: base (value)
{
_multiplier = multiplier;
}
public override void Initialize(Task task)
{
task.AccessMe = _value * _multiplier;
}
}
public class Task
{
public Task()
{
}
public int AccessMe { get; set; }
public void OnEnterTask(ITaskArgument args)
{
args.Initialize(this);
}
}
example
SimpleTaskArgument simpleArgs = new SimpleTaskArgument(10);
ComplexTaskArgument complexArgs = new ComplexTaskArgument(10, 3);
Task task = new Task();
task.OnEnterTask(simpleArgs);
Console.WriteLine(task.AccessMe); // would display 10
task.OnEnterTask(complexArgs);
Console.WriteLine(task.AccessMe); // would display 30

OK, changed my answer a bit in light of the changing requirements appearing in the comments! (Sheesh, scope creep or what?!)
public class Task
{
public int Variable1 { get; internal set; }
public int Variable2 { get; internal set; }
public void OnEnterTask(ITaskInitializer initializer)
{
initializer.Initialize(this);
}
}
public interface ITaskInitializer
{
void Initialize(Task task);
}
public class SimpleTaskInitializer : ITaskInitializer
{
private int uGotIt = 10;
public void Initialize(Task task)
{
task.Variable1 = uGotIt;
}
}
public class ComplexTaskInitializer : ITaskInitializer
{
private int uGotIt = 10;
private int multiplier = 10;
public void Initialize(Task task)
{
task.Variable1 = uGotIt;
task.Variable2 = uGotIt * multiplier;
// etc - initialize task however required.
}
}

You could create overloads of Task as one option:
public class SimpleTask : Task
{
public override void EnterTask(TaskArgument arg)
{
var s = (SimpleTaskArgument)arg;
}
}
So each task type deals with an equivalent argument type. Or, you can move the logic to a TaskFactory with a static method that returns an int, and has the type checking argument there.
public static class TaskFactory
{
public static int GetVal(TaskArgument arg)
{
if (args is SimpleTaskArgument) {
return ((SimpleTaskArgument)args).uGotIt;
} else if (args is ComplexTaskArgument) {
return ((ComplexTaskArgument)args).uGotItValue * ((ComplexTaskArgument)args).multiplier;
}
}
}
Your interface implementation also would work; I wouldn't discount that... or define an abstract method within Taskargument, that each overrides to return the value.
HTH.