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How to pass value in ArrayList from method to method

public Program()
{
amount_bike = new ArrayList();
}
public void push(int value)
{
this.amount_bike.Add(value);
}
public int amount_bike_pop()
{
if (this.amount_bike.Count == 0)
{
return -100000;
}
int lastItem = (int)this.amount_bike[this.amount_bike.Count - 1];
this.amount_bike.RemoveAt(this.amount_bike.Count - 1);
return lastItem;
}
public static void Bike_status()
{
bool exit = false;
Program available = new Program();
available.push(0);
available.push(0);
available.push(50);
WriteLine("E-bike available for rent is : " + available.amount_bike_pop() + " bikes.");
WriteLine("Rented E-bike is : " + available.amount_bike_pop() + " bikes.");
WriteLine("Broke E-bike is : " + available.amount_bike_pop() + " bikes.");
WriteLine("\n");
WriteLine("Please enter a number: 1 is back to pervoius menu or 0 to Exit");
int input = Convert.ToInt32(ReadLine());
while (exit == false)
{
if (input == 1)
{
Clear();
exit = true;
continue;
}
else if (input == 0)
{
Clear();
Exit();
}
else
{
Clear();
Bike_status();
}
}
}
public static void Add_bike()
{
}
I study data structures and Algorithms. In this code, I keep the value in an ArrayList named "available" in the Bike_status method. I need to pass a value in an ArrayList to the Add_bike method. How do I pass a value from one method to another? Actually, I need to pass valus such as 50 to plus some number that I push in Console.ReadLine.

Try to slow down.at starting point of programming sometimes it's confusing.
How do I pass a value from one method to another?
The simple answer is easy ,you want something to use in the function then in your method(s) you create parameter and pass the things you want to it.
like
//edit method to get int value -> public static void Bike_status()
public static void Bike_status(int value)
//edit when to call
else
{
Clear();
Bike_status(input);//send int value in
}
But really, what is that do you really want to learn?
if it OOP? I recommend you study this
https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/object-oriented/
To put it simply you has bicycle shop class separate from main program then use the method in that class
e.g.
//bicycle class
public class Bicycles{
public int ID {get;set;}
pulibc string status {get;set; }
public Bicycles(int p_id, string p_status)
{
ID = p_id;
status=p_status;
}
}
//bicycle shop class
public class BicyclesShop{
public List<Bicycle> available {get;set;} // class member
public BicyclesShop() // go search keyword "constructor"
{
available = new List<Bicycle> ();
}
//other method
public void Add_bike()
{
// I can access available object !
// do anything with this class member(s) !
}
public void Bike_status(int inputVal)
{
// do something with inputVal , change some properties?
}
//other methods
public int amount_bike_pop()
{
return available.Count();
}
public int amount_bike_broken_pop()
{
return available.Where(o=>o.status =="Broken").Count(); // go search linq
}
}
//To use in Main program method
BicyclesShop bs =new BicyclesShop();
bs.available.Add( new Bicycle(1 ,"OK") ); //add bicycle #1 in list
bs.available.Add( new Bicycle(2),"Broken" ); //add bicycle #2 in list
WriteLine("Broke E-bike is : " + bs.amount_bike_broken_pop() + " bikes.");

problem with my array class error CS0120 C# [duplicate]

This question already has answers here:
CS0120: An object reference is required for the nonstatic field, method, or property 'foo'
(9 answers)
Closed 3 years ago.
I'm still learning to code so if there are some issues, please tell me! This is for a school essay.
I'm writing a code that asks some information about a game: game name, the devs behind it, the publisher, and its cost.
The essay has multiple different tasks, like: make a program that uses get set, arrays, methods, or and so on. I made it all into a program, and I got stuck with the error
CS0120 An object reference is required for the non-static field, method, or property 'Program.gameInfoArray'
The code:
class Program
{
//the class array that stores the games
public gameInfo[] gameInfoArray = new gameInfo[10];
static void Main(string[] args)
{
bool done = false;
// this is where i get the issue
for (int i = 0; i >= gameInfoArray.Length || done == false; i++)
{
//asks what the game is called
Console.WriteLine("What is the game called:");
string gameName = Console.ReadLine();
//asks who the devolopers are
Console.WriteLine("Who where the devolopers behind the game:");
string devoloper = Console.ReadLine();
//asks who published the game
Console.WriteLine("Who released the game:");
string publisher = Console.ReadLine();
//ask how much the game costs
Console.WriteLine("How much does the game cost:");
string cost = Console.ReadLine();
//inputs the information in to the class array, this is also where i get the issue
gameInfoArray[i].gameInformationGrabber(gameName, devoloper, publisher, cost);
//asks if the
Console.WriteLine("are there any more games? Y/N");
while(true)
{
ConsoleKeyInfo yesOrNo = Console.ReadKey();
if ((yesOrNo.KeyChar == 'Y') || (yesOrNo.KeyChar == 'y'))
{
done = true;
break;
}
else if ((yesOrNo.KeyChar == 'N') || (yesOrNo.KeyChar == 'n'))
{
break;
}
}
}
}
}
The script:
class gameInfo
{
private string gameName;
private string devoloper;
private string publisher;
private string cost;
public void gameInformationGrabber(string game, string dev, string publisher, string cost)
{
theGameName = game;
theDevs = dev;
thePublisher = publisher;
theCost = cost;
}
public string theGameName
{
get { return gameName; }
set { gameName = value; }
}
public string theDevs
{
get { return devoloper; }
set { devoloper = value; }
}
public string thePublisher
{
get { return publisher; }
set { publisher = value; }
}
public string theCost
{
get { return cost; }
set { cost = value; }
}
}
Thanks a ton in advance. Sorry if I messed up big time somewhere in the code.

You've got two comment, it is perfect solution for you.
I hope you spend a time to get a basic concept from it.
However, this will help you.
1. Static only
This is a solution mentioned comment.
class Program
{
// Add static keyword. Because Main() method is static.
// So, every variable inside it should be static.
// public gameInfo[] gameInfoArray = new gameInfo[10];
public static gameInfo[] gameInfoArray = new gameInfo[10];
static void Main(string[] args)
{
......
}
}
2. Work with local variable
class Program
{
//public gameInfo[] gameInfoArray = new gameInfo[10];
static void Main(string[] args)
{
// Declare as local variable.
// In static method will now complain using local variable.
gameInfo[] gameInfoArray = new gameInfo[10];
......
}
}
I've tried to run this code, plase don't forget initialize gameInfoArray to prevent null reference exception.
you may need this before entering for loop,
for (int index = 0; index < gameInfoArray.Length; index++)
{
gameInfoArray[index] = new gameInfo();
}

Beginner to Array c#

I don't really understand arrays and I need to create a variable of type 'array of songs' then initialize it to a new Array so it can store 4 references to Songs. How would I then create a loop that would run enough times to fill the array whilst calling the InputSOngDetails() method and store the return value in that method?
namespace Songs
{
class Program
{
static void Main(string[] args) {
InputSongDetails();
}
static Song InputSongDetails()
{
Console.WriteLine("What is the name of your song");
string name = Console.ReadLine();
Console.WriteLine("What is the artists name");
string artist = Console.ReadLine();
int records;
Console.WriteLine("How many records did it sell");
while (!int.TryParse(Console.ReadLine(), out records) || records < 0)
{
Console.WriteLine("That is not valid please enter a number");
}
return new Song(name, artist, records);
}
}
}
This is my Songs class if needed
namespace Songs
{
class Song
{
string name;
string artist;
int copiesSold;
public Song(string name, string artist, int copiesSold)
{
this.name = name;
this.artist = artist;
this.copiesSold = copiesSold;
}
public Song()
{
}
public string GetArtist()
{
return artist;
}
public string GetDetails()
{
return $"Name: {name} Artist: {artist} Copies Sold: {copiesSold},";
}
public string GetCertification()
{
if (copiesSold<200000)
{
return null;
}
if (copiesSold<400000)
{
return "Silver";
}
if (copiesSold<600000)
{
return "gold";
}
return "Platinum";
}
}
}

Fist, initialize your array of songs with new Song[ length ], then a simple for-loop will suffice.
static void Main(string[] args)
{
Song[] songs = new Song[4];
for(int i = 0; i < songs.Length; i++)
{
songs[i] = InputSongDetails();
}
}
Or as the commenters suggest, just use a variable-length List<Song>.
static void Main(string[] args)
{
List<Song> songs = new List<Song>();
for(int i = 0; i < 4; i++)
{
songs.Add(InputSongDetails());
}
}
Once you've mastered the basics, you can also accomplish this with a bit of Linq (though I wouldn't actually recommend it in this case):
static void Main(string[] args)
{
var songs = Enumerable.Range(0, 4)
.Select(i => InputSongDetails())
.ToList();
}

This is not really an answer as much as it is a tip for getting input from the user in a console application which might be useful to you (well, the answer is in the last code snippet, but p.s.w.g has already covered that very well).
Since an interactive console session usually ends up with a lot of Console.WriteLine("Ask the user a question"); string input = Console.ReadLine();, and, as you've already done very well, include some validation on the input in some cases, I've found it handy to write the following methods below.
Each of them take in a string, which is the prompt for the user (the question), and return a strongly-typed variable that represents their input. Validation (when needed) is all done in a loop in the method (as you've done):
private static ConsoleKeyInfo GetKeyFromUser(string prompt)
{
Console.Write(prompt);
var key = Console.ReadKey();
Console.WriteLine();
return key;
}
private static string GetStringFromUser(string prompt)
{
Console.Write(prompt);
return Console.ReadLine();
}
public static int GetIntFromUser(string prompt = null)
{
int input;
int row = Console.CursorTop;
int promptLength = prompt?.Length ?? 0;
do
{
Console.SetCursorPosition(0, row);
Console.Write(prompt + new string(' ', Console.WindowWidth - promptLength - 1));
Console.CursorLeft = promptLength;
} while (!int.TryParse(Console.ReadLine(), out input));
return input;
}
With these methods in place, getting input is as simple as:
string name = GetStringFromUser("Enter your name: ");
int age = GetIntFromUser("Enter your age: ");
And it makes writing the method to get a Song from the user that much easier:
private static Song GetSongFromUser()
{
return new Song(
GetStringFromUser("Enter song name: "),
GetStringFromUser("Enter Artist name: "),
GetIntFromUser("Enter number of copies sold: "));
}
So now our main method just looks like (and this is the answer to your question):
private static void Main()
{
var songs = new Song[4];
for (int i = 0; i < songs.Length; i++)
{
songs[i] = GetSongFromUser();
}
Console.WriteLine("\nYou've entered the following songs: ");
foreach (Song song in songs)
{
Console.WriteLine(song.GetDetails());
}
GetKeyFromUser("\nDone! Press any key to exit...");
}
Additionally, here are some suggestions for improving the Song class.

IEnumerable - Move Next

I have an IEnumerable from which I need to fetch each item and display it one by one. The displaying is not a continuous process..i.e I should fetch one item and display it on the UI, then wait for some user feedback on that item, and then move on to the next item. For example from the below code, I need to fetch a question, then display it to the user, then user hits enter, and then I move on to fetching the next question.
My Question is how do I do that? Is IEnumerable the best way of achieving this or should I revert to list and start storing the indexes and increment it one by one?
Please note that I'm using .NET 3.5.
Code:
class Program
{
static void Main(string[] args)
{
Exam exam1 = new Exam()
{
Questions = new List<Question>
{
new Question("question1"),
new Question("question2"),
new Question("question3")
}
};
var wizardStepService = new WizardStepService(exam1);
var question = wizardStepService.GetNextQuestion();
//Should output question1
Console.WriteLine(question.Content);
Console.ReadLine();
//Should output question2 but outputs question1
question = wizardStepService.GetNextQuestion();
Console.WriteLine(question.Content);
Console.ReadLine();
//Should output question3 but outputs question1
question = wizardStepService.GetNextQuestion();
Console.WriteLine(question.Content);
Console.ReadLine();
}
}
public class Question
{
private readonly string _text;
public Question(string text)
{
_text = text;
}
public string Content { get { return _text; } }
}
internal class Exam
{
public IEnumerable<Question> Questions { get; set; }
}
internal class WizardStepService
{
private readonly Exam _exam;
public WizardStepService(Exam exam)
{
_exam = exam;
}
public Question GetNextQuestion()
{
foreach (var question in _exam.Questions)
{
//This always returns the first item.How do I navigate to next
//item when GetNextQuestion is called the second time?
return question;
}
//should have a return type hence this or else not required.
return null;
}
}

Yes, GetEnumerator() should work fine; although strictly speaking you need to handle Dispose():
internal class WizardStepService : IDisposable
{
private IEnumerator<Question> _questions;
public WizardStepService(Exam exam)
{
_questions = exam.Questions.GetEnumerator();
}
public void Dispose()
{
if (_questions != null) _questions.Dispose();
}
public Question GetNextQuestion()
{
if (_questions != null)
{
if (_questions.MoveNext())
{
return _questions.Current;
}
Dispose(); // no more questions!
}
//should have a return type hence this or else not required.
return null;
}
}
and also:
using (var wizardStepService = new WizardStepService(exam1))
{
var question = wizardStepService.GetNextQuestion();
//Should output question1
Console.WriteLine(question.Content);
Console.ReadLine();
//Should output question2 but outputs question1
question = wizardStepService.GetNextQuestion();
Console.WriteLine(question.Content);
Console.ReadLine();
//Should output question3 but outputs question1
question = wizardStepService.GetNextQuestion();
Console.WriteLine(question.Content);
Console.ReadLine();
}
However, since you're not actually testing the result each time, you could also do something like:
using (var questions = exam1.Questions.GetEnumerator())
{
questions.MoveNext();
var question = questions.Current;
//Should output question1
Console.WriteLine(question.Content);
Console.ReadLine();
//Should output question2 but outputs question1
questions.MoveNext();
question = questions.Current;
Console.WriteLine(question.Content);
Console.ReadLine();
//Should output question3 but outputs question1
questions.MoveNext();
question = questions.Current;
Console.WriteLine(question.Content);
Console.ReadLine();
}
Or as a final thought, perhaps just:
var questions = exam1.Questions.Take(3).ToArray();
//Should output question1
Console.WriteLine(questions[0].Content);
Console.ReadLine();
//Should output question2 but outputs question1
Console.WriteLine(questions[1].Content);
Console.ReadLine();
//Should output question3 but outputs question1
Console.WriteLine(questions[2].Content);
Console.ReadLine();

Well you could store an IEnumerator<T> instead, and change GetNextQuestion to:
return _exam.MoveNext() ? _exam.Current : null;
However, at that point you're not actually adding any value with the Exam or WizardStepService classes, and you might as well just use IEnumerator<T> directly in Main. Note that your Main method itself is a little odd - it has repeated code where a foreach loop would be simpler - and you're unconditionally asking three questions.
Note that if you have a type with an IEnumerator<T> as a field, you probably want to implement IDisposable in order to dispose of the iterator, too - it all gets a bit messy.

Try this:
class Program2
{
static void Main(string[] args)
{
Exam exam1 = new Exam()
{
Questions = new List<Question>
{
new Question("question1"),
new Question("question2"),
new Question("question3")
}
};
var wizardStepService = new WizardStepService(exam1);
foreach (var question in wizardStepService.GetQuestions())
{
Console.WriteLine(question.Content);
Console.ReadLine();
}
}
}
public class Question
{
private readonly string _text;
public Question(string text)
{
_text = text;
}
public string Content
{
get
{
return _text;
}
}
}
internal class Exam
{
public IEnumerable<Question> Questions
{
get;
set;
}
}
internal class WizardStepService
{
private readonly Exam _exam;
public WizardStepService(Exam exam)
{
_exam = exam;
}
public IEnumerable<Question> GetQuestions()
{
foreach (var question in _exam.Questions)
{
//This always returns the first item.How do I navigate to next
//item when GetNextQuestion is called the second time?
yield return question;
}
//should have a return type hence this or else not required.
//return null;
}
}

I need a simple and elegant user validation technique for a c# console application

Coming from a procedural background, I'm running into a conceptual block while designing a menu-based console application and user input validation. My goal is to display a menu that launches other processes. I want to limit user input to 1, 2, or 3 at the menu.
In a procedural language, I would do something like this pseudocode:
10 print "Make a choice"
20 choice = [dataFromKeyboard]
30 if choice < 4 && choice > 0
40 then 10
50 else 60
60 process valid choices
and no matter what I try, I can't get that out of my head while designing an OO program. Consider (simplified to include only 3 menu items):
class Menu
{
public static void Main(String[] args)
{
DisplayMenu thisdm = new DisplayMenu;
int menuChoice = thisdm.displayMenu();
ProcessMenu thispm = new ProcessMenu();
thispm.processMenu(menuChoice);
}
}
class DisplayMenu
{
public int displayMenu()
{
Console.WriteLine("1 - foo3");
Console.WriteLine("2 - foo2");
Console.WriteLine("3 - foo3");
Console.WriteLine("choose");
String choice = Console.ReadLine();
int intChoice = Convert.ToInt32(choice);
return intChoice;
}
}
class ProcessMenu
{
public void processMenu(int choice)
{
switch(choice)
{
case 1:
foo1();
break;
case 2:
foo2();
break;
case 3:
foo3();;
break;
default:
Console.WriteLine("Invalid selection. Please select 1, 2, or 3.");
break;
}
}
}
So here's where I'm stuck. I just can't wrap my head around a simple and elegant way validate my user input that's from an OO rather than procedural standpoint.
Assuming I do the validation in the DisplayMenu, I would be validating after the input is read. But if it turns out to be invalid, how do I re-ask for valid input, since I've already called displayMenu method from Main?
I've been playing with while loops for about an hour, something like this:
intChoice = 0;
[print the menu]
while ((intChoice<1) || (intChoice>3))
Console.WriteLine("Please make a valid choice from the menu");
choice = Console.ReadLine();
etc.
but can't seem to find the sweet spot where I can control user input.
I suspect it's because I'm thinking to procedurally, and not object-oriented enough. Anyone have any tips or input to help me wrap my head around this?

Expanding on #AlexeiLevenkov's suggestion of "turning your classes 90 degrees", I went a step further and created this example of a "Modular" console Application:
class Program
{
static void Main(string[] args)
{
//Retrieve all Module types in the current Assembly.
var moduletypes = Assembly.GetExecutingAssembly()
.GetTypes()
.Where(x => x.IsSubclassOf(typeof(ConsoleModule)));
//Create an instance of each module
var modules = moduletypes.Select(Activator.CreateInstance)
.OfType<ConsoleModule>()
.OrderBy(x => x.Id)
.ToList();
int SelectedOption = -1;
while (SelectedOption != 0)
{
//Show Main Menu
Console.Clear();
Console.WriteLine("Please Select An Option:\n");
modules.ForEach(x => Console.WriteLine(string.Format("{0} - {1}", x.Id, x.DisplayName)));
Console.WriteLine("0 - Exit\n");
int.TryParse(Console.ReadLine(), out SelectedOption);
//Find Module by Id based on user input
var module = modules.FirstOrDefault(x => x.Id == SelectedOption);
if (module != null)
{
//Execute Module
Console.Clear();
module.Execute();
Console.WriteLine("Press Enter to Continue...");
Console.ReadLine();
}
}
}
ConsoleModule class:
public abstract class ConsoleModule
{
public int Id { get; set; }
public string DisplayName { get; set; }
public abstract void Execute();
}
Some sample Modules:
public class EnterUserNameModule : ConsoleModule
{
public EnterUserNameModule()
{
Id = 2;
DisplayName = "User Name";
}
public static string UserName { get; set; }
public override void Execute()
{
Console.WriteLine("Please Enter Your Name: ");
UserName = Console.ReadLine();
}
}
public class HelloWorldModule: ConsoleModule
{
public HelloWorldModule()
{
Id = 1;
DisplayName = "Hello, World!";
}
public override void Execute()
{
Console.WriteLine("Hello, " + (EnterUserNameModule.UserName ?? "World") + "!");
}
}
public class SumModule: ConsoleModule
{
public SumModule()
{
Id = 3;
DisplayName = "Sum";
}
public override void Execute()
{
int number = 0;
Console.Write("Enter A Number: ");
if (int.TryParse(Console.ReadLine(), out number))
Console.WriteLine("Your number plus 10 is: " + (number + 10));
else
Console.WriteLine("Could not read your number.");
}
}
Result:
It uses a little bit of reflexion to find all types deriving from ConsoleModule in the current assembly, then shows a menu with all these options (which are actually properties in this class), and calls the Execute() method when an appropiate option is selected. Much more towards OO way of thinking.

Make your processMenu function return some kind of indicator. You could use exceptions for this instead, but that's overkill.
public bool processMenu(int choice)
{
....
}
If the choice was acceptable, then return true, otherwise return false. Then:
public static void Main(String[] args)
{
DisplayMenu thisdm = new DisplayMenu;
ProcessMenu thispm = new ProcessMenu();
int menuChoice;
do {
menuChoice = thisdm.displayMenu();
} while( !thispm.processMenu(menuChoice) );
}

The way you are doing should be changed. Anyhow, for the same as your question, this works out:
DisplayMenu thisdm = new DisplayMenu();
int menuChoice = -1;
while (menuChoice < 1 || menuChoice > 3)
{
Console.WriteLine("enter valid choice");
menuChoice = thisdm.displayMenu();
}
ProcessMenu thispm = new ProcessMenu();
thispm.processMenu(menuChoice);

the code like:
class Program
{
static void Main(string[] args)
{
DisplayMenu thisdm = new DisplayMenu();
ProcessMenu thispm = new ProcessMenu();
thisdm.displayMenu();
int menuChoice = thispm.GetChoice();
thispm.processMenu(menuChoice);
Console.Read();
}
}
class DisplayMenu
{
public void displayMenu()
{
Console.WriteLine("1 - foo3");
Console.WriteLine("2 - foo2");
Console.WriteLine("3 - foo3");
Console.WriteLine("choose");
}
}
class ProcessMenu
{
public int GetChoice()
{
String choice = Console.ReadLine();
int intChoice = Convert.ToInt32(choice);
while (!Validate(intChoice))
{
Console.WriteLine("Invalid selection. Please select 1, 2, or 3.");
choice = Console.ReadLine();
intChoice = Convert.ToInt32(choice);
}
return intChoice;
}
public void processMenu(int choice)
{
switch (choice)
{
case 1:
//foo1();
break;
case 2:
//foo2();
break;
case 3:
//foo3(); ;
break;
default:
//Console.WriteLine("Invalid selection. Please select 1, 2, or 3.");
break;
}
}
private int[] forChoices=new int[]{1,2,3};
private bool Validate(int choice)
{
if(forChoices.Contains(choice))
{
return true;
}
return false;
}
}