Why can only auto-implemented properties can have initializers in C#? - c#

I get the "only auto-implemented properties can have initializers in C#" error when trying to do the following:
public int Precision
{
get { return Precision; }
set
{
if (value < 0)
Precision = 0;
else if (value > 15)
Precision = 15;
else
Precision = value;
}
} = 12;
Why is this not allowed?

Pretty sure that is not really how you use get and set. Plus your get suffers from self reference. I think this is what you want:
private int _precision = 12;
public int Precision {
get => _precision;
set {
if (value < 0)
_precision = 0;
else if (value > 15)
_precision = 15;
else
_precision = value;
}
}

Well, an auto-property is just syntactic sugar for a property that gets and sets an automatically created backing-field. So the following two code-segments are similar:
public int Precision { get; set; }
and
public int Precision
{
get { return <Precision>k__BackingField; }
set { <Precision>k__BackingField = value; }
}
However when you create some own logic within your property, there´s no such thing as an automatically backing-field. In fact you could even do the following without any backing-field:
set { Console.WriteLine(); }
An initial value however is resolved to the following constructor:
MyClass()
{
this.<Precision>k__BackingField = myValue;
}
However when there is no such backing-field, what should the compiler do here?

Related

How to set the Value variable of this custom Odin Inspector class

I know, the title is bad, but I couldn't think if a better one. The question is very specific.
Ok, so I'm using a class in my game identical to Odin Inspector's example RPG Skills classes. But it's set up in a way I don't quite understand and I can't work out how to set the value (I can get it, and there is a setter, so it's possible to set too). Also, all the skill classes/structs/etc are in the same .cs file.
The SkillList function I use to get the Value:
(I get it with skills[Strength].Value; in other classes)
public int this[SkillType type]
{
get
{
for (int i = 0; i < this.skills.Count; i++)
{
if (this.skills[i].Type == type)
return this.skills[i].Value;
}
return 0;
}
set
{
for (int i = 0; i < this.skills.Count; i++)
{
if (this.skills[i].Type == type)
{
var val = this.skills[i];
val.Value = value;
this.skills[i] = val;
return;
}
}
this.skills.Add(new SkillValue(type, value));
}
}
SkillValue struct:
[Serializable]
public struct SkillValue : IEquatable<SkillValue>
{
public SkillType Type;
public int Value;
public SkillValue(SkillType type, int value)
{
this.Type = type;
this.Value = value;
}
public SkillValue(SkillType type)
{
this.Type = type;
this.Value = 0;
}
public bool Equals(SkillValue other)
{ return this.Type == other.Type && this.Value == other.Value; }
}
SkillType enum:
public enum SkillType
{
Science,
Technology,
Arts,
Language,
}
I've tried:
skills[Science].Value = 10;
skills[Science] = new SkillValue(Science, 10);
skills[Science, 10]; (using a new function made by me)
skills[Science](10);
skills[Science].Value(10);
skills[Science] = 10;
But none work, and I'm just guessing randomly now.
How can I set the value?
Thanks
The solution:
character.skills[Rorschach.Character.Skills.SkillType.Science] = value;
Your property is of type int and expects a key of type SkillType so it should probably be
SkillList skills;
skills[SkillType.Science] = 10;
actually also
I get it with skills[Strength].Value;
seems odd with the code you provided. As said the property returns an int which has no property Value so it should actually be
int x = skills[SkillType.Strength];
Now knowing the full implementation code and your actual usage:
public SkillList skills;
...
public int Science
{
get { return this.Character.skills[Science].Value; }
set { this.Character.skills[Science].Value(10); }
}
ATTENTION!
What you did here by accident is using the other property
public SkillValue this[int index]
{
get { return this.skills[index]; }
set { this.skills[index] = value; }
}
which takes an int index and returns a SkillValue.
BUT you are causing a runtime StackOverlowExeption due to a recursive call of Science.
You can't use Science inside of the getter or setter of equally called property!
Imagine using the getter as example:
You would call
var test = Science;
so it executes the getter
return Character.skills[Science].Value;
but well ... in order to know the value of Science in order to use it here as the index it would again have to execute the getter so again
return Character.skills[Science].Value;
and by now you hopefully get what I mean.
Solution
You property should actually as guessed before rather look like
public int Science
{
get { return Character.skills[SkillType.Science]; }
set { Character.skills[SkillType.Science] = value; }
}

How to assign a value to a field in different class?

In this program, I have 2 classes Application and Customer. I want to initialize Standard Fare with some value which should be entered by the user. Standard Fare field is in Customer class.
I did this, but it is not showing the desired result. When Calculate function is called The Value of Standard fare is becoming zero.
When I initialize the value of STANDARD_FARE in Customer class itself, then the program is working as desired.
How can I input the value given by the user to STANDARD_FARE?
Also methods like GetAge(), GetPassNo() in Application class is not returning the value of the same.
class Application
{
private static int Nop ;
private static double TotalFare=0;
Customer cust= new Customer();
static void Main(string[] args)
{
Application obj = new Application();
Console.Write("Enter the STANDARD RATE of the tour ");
obj.cust.StandardFare = int.Parse(Console.ReadLine());
a:
Console.Clear();
Console.WriteLine("Enter the number of passengers");
Nop = int.Parse(Console.ReadLine());
Application[] app = new Application[Nop];
if (Nop <= 0)
{
Console.WriteLine("Please enter a valid number of passengers");
Console.ReadKey();
goto a;
}
for (int i = 0; i < Nop; i++)
{
app[i] = new Application();
app[i].GetInformationFromCust();
}
for (int j = 0; j < Nop; j++)
{
app[j].cust.Display();
}
}
public int GetInformationFromCust()
{
b:
Console.Clear();
int slen = 0;
Console.WriteLine("Enter the title of the passenger");
cust.Customer_Title = Console.ReadLine();
Console.WriteLine("\r\nEnter passenger's First name :");
cust.Customer_FName = Console.ReadLine();
Console.WriteLine("\r\nEnter passenger's Last name :");
cust.Customer_LName = Console.ReadLine();
slen = cust.Customer_FName.Length + cust.Customer_LName.Length;
if (slen < 5 || slen > 15)
{
Console.WriteLine("\r\nName should be between 5 to 15 characters, Please try again ");
Console.ReadLine();
goto b;
}
c:
long x = 0, len = 0;
Console.WriteLine("\r\nEnter the passport number of the passenger ");
cust.CustomerPassNo = int.Parse(Console.ReadLine());
x = cust.CustomerPassNo;
while (x > 0)
{
x = x / 10;
++len;
}
if (len != 8)
{
Console.WriteLine("\r\nInvalid passport number, passport should be of 8 digits ");
goto c;
}
d:
Console.WriteLine("\r\nEnter the age of the passenger :");
cust.Customer_Age = int.Parse(Console.ReadLine());
if (cust.Customer_Age < 0)
{
Console.WriteLine("\r\nInvalid age, please enter a valid age ");
goto d;
}
cust.CalculatePrice();
return 0;
}
public int GetAge()
{
return cust.Customer_Age;
}
public double GetAirFare()
{
return cust.CustomerTicket ;
}
public long GetPassportNo()
{
return cust.CustomerPassNo;
}
public string GetTitle()
{
return cust.Customer_Title;
}
}
class Customer
{
const double K_DISCOUNT = 0.10;
const double S_DISCOUNT = 0.20;
private double STANDARD_FARE;
private string CustomerName { get; set; }
private int CustomerAge;
private string CustomerFName;
private string CustomerLName;
private long CustomerPassport;
private double CustomerPrice;
private string CustomerTitle;
private double KidDiscount;
private double SeniorDiscount;
public Customer()
{
this.KidDiscount = K_DISCOUNT;
this.SeniorDiscount = S_DISCOUNT;
}
public double StandardFare
{
get { return STANDARD_FARE; }
set { STANDARD_FARE = value; }
}
public int Customer_Age
{
get { return CustomerAge; }
set { CustomerAge = value; }
}
public string Customer_Title
{
get { return CustomerTitle; }
set { CustomerTitle = value; }
}
public string Customer_FName
{
get { return CustomerFName; }
set { CustomerFName = value; }
}
public string Customer_LName
{
get { return CustomerLName; }
set { CustomerLName = value; }
}
public long CustomerPassNo
{
get { return CustomerPassport; }
set { CustomerPassport = value; }
}
public double CustomerTicket
{
get { return CustomerPrice; }
set { CustomerPrice = value; }
}
public int CalculatePrice()
{
if (CustomerAge < 3)
{
CustomerPrice = 0;
}
else if (CustomerAge >= 3 && CustomerAge < 18)
{
CustomerPrice = STANDARD_FARE - (STANDARD_FARE * KidDiscount);
}
else if (CustomerAge > 65)
{
CustomerPrice = STANDARD_FARE - (STANDARD_FARE * SeniorDiscount);
}
else
{
CustomerPrice = STANDARD_FARE;
}
return 0;
}
public void Display()
{
//some code here
}
}
You are populating your array app with instances of Application that still have the default STANDARD_FARE value (which is 0.0), because you have never set it on those instances. You only set it on the obj.cust instance, which you never again use. Because STANDARD_FARE is an instance variable, changes to it have no affect on other (or future) instances.
You have the same problem in reverse with all the Application.Get* functions; they are getting properties of an object (obj.cust) that has never had any properties set, other than StandardFare/STANDARD_FARE.
The most obvious fix is to do away with obj and obj.cust entirely - they have no use other than to be confusing - and make STANDARD_FARE a static variable (and its setter StandardFare a static property).
BTW, your naming conventions are terrible and inconsistent; if I were your grader I'd dock you points for using unclear variable names(app, nop), and for using ALL_CAPS for non-constants (STANDARD_FARE). I'd also object to using a private auto-backed property (CustomerName, which is also never used) instead of simply a private variable, for not using auto-backed properties elsewhere (StandardFare as an explicitly-coded public getter and setter for STANDARD_FARE, etc.), and for copying constant values into non-settable instance variables (K_DISCOUNT to KidDiscount; just use the constant directly, or at least make KidDiscount static and add some non-private access to it). As others have mentioned, you of course should not be using goto in place of loops. I'll also mention the error-prone and inefficient checking the length of the passport number by repeated division instead of simply checking whether it's less than 99999999 (in theory, passport numbers might start with a zero, which would look like less than 8 digits after parsing, but you could also make sure it's greater than 10000000 if you want).

Updating Total causing infinite loop

I current have 3 telerik:RadMaskedCurrencyInput.
The first one is the principal
The First and Second are the disbursals
At the moment I have it set up such that principal = First disbursal + Second disbursal.
I'm trying to have a case such that if I update principal it updates First Disbursal and sets second disbursal to zero. So Principal = DisbursalOne and DisbursalTwo = 0
// Pv is principal
private decimal?_pv;
public decimal? Pv { get { return _pv; } set { _pv = value; OnPropertyChanged("Pv"); } }
private decimal? _disbursalOne;
public decimal? DisbursalOne
{
get
{
return _disbursalOne;
}
set
{
_disbursalOne = value;
if (_disbursalOne != null)
DisbursalTotal = _disbursalOne + DisbursalTwo;
else
{
_disbursalOne = 0;
}
OnPropertyChanged("DisbursalOne");
}
}
Disbursal Two essentially almost identical to Disbursal one so the Code is not necessary.
private decimal? _disbursalTotal;
public decimal? DisbursalTotal
{
get { return _disbursalTotal; }
set
{
_disbursalTotal = value;
if (_disbursalTotal != null) UpdateDisbursalTotal(_disbursalTotal);
else UpdateDisbursalTotal(0);
Pv = _disbursalTotal;
OnPropertyChanged("DisbursalTotal");
}
}
I apologize for the bad title.
// Updates the Total Disbursed Fields on the UI
public void UpdateDisbursalTotal(decimal? Total)
{
var cultureInfo = Thread.CurrentThread.CurrentCulture; // You can also hardcode the culture, e.g. var cultureInfo = new CultureInfo("fr-FR"), but then you lose culture-specific formatting such as decimal point (. or ,) or the position of the currency symbol (before or after)
var numberFormatInfo = (NumberFormatInfo)cultureInfo.NumberFormat.Clone();
numberFormatInfo.CurrencySymbol = "$"; // Replace with "$" or "£" or whatever you need
Double _total = (double) Total;
DisburseString = _total.ToString("C", numberFormatInfo);
}
private string _disburseString;
public string DisburseString { get { return _disburseString; } set { _disburseString = value; OnPropertyChanged("DisburseString"); } }
It's usually a good idea to format your PropertyChanged events in the following way, that way if the same value gets set, you don't notify anyone as nothing has actually changed. If things are relying on your PropertyChanged events to update each other, this should break the cycle:
private decimal? _disbursalTotal;
public decimal? DisbursalTotal
{
get { return _disbursalTotal; }
set
{
if (value != _disburseTotal) {
_disbursalTotal = value;
if (_disbursalTotal != null) UpdateDisbursalTotal(_disbursalTotal);
else UpdateDisbursalTotal(0);
Pv = _disbursalTotal;
OnPropertyChanged("DisbursalTotal");
}
}
}
Step through the code. My guess is that OnPropertyChanged event also changes a property. You can check if the property is actually changing (or just being set to the same value) before calling OnPropertyChanged.

How to use get and set for array element in C#?

I have the following class:
public class test
{
private int i;
public test(int in)
{
i = in;
}
public int testint;
{
get { return i; }
set { i = testint; }
}
}
And the following code:
test[] data = new test[3];
for(int j = 0; j < 3; j++)
{
data[i] = new test(0);
data[i].testint = int.Parse(Console.ReadLine());
}
Console.WriteLine(test[0].testint);
Console.WriteLine(test[1].testint);
Console.WriteLine(test[2].testint);
When I run this program and type in 1, 2, 3 as the input, the output is 0, 0, 0. I don't understand why the get or set seem to be not working. If I initialize the array elements with a value other than 0, the output will be that. The data[i].testint = int.Parse(Console.ReadLine()); seems to not be working. How would I go about doing something like that?
Change the set method to this:
public int testint
{
get { return i; }
set { i = value; }
}
You setter is incorrect. It should be:
set { i = value; }
You had:
set { i = testint; }
Which only triggers the getter, which gets from i, so in the end your setter was doing i = i .
In a setter, the value keyword contains the new candidate value for the property. value's type equals the property's. I say candidate value because you can validate it and choose to not apply it.
In your case, you were not applying the value.
Update
Also, when defining getters and setters, no semicolon should be used. Code, then, would look like this:
public int testint
{
get { return i; }
set { i = value; }
}
I see two errors in this code:
public int testint;
{
get { return i; }
set { i = testint; }
}
There should be no semicolon after testint at the top. Also, set needs to assign using value, like this:
public int testint
{
get { return i; }
set { i = value; }
}
Change your setter to say:
set { i = value; }
value corresponds to the value you send to set the variable.
Here's simple way.
public int TestInt {get; set;}

C# StackOverflowException

Problem: I am trying to update a List. If a certain item's ID already exists in the List, I want to add onto that item's quantity. If not, then I want to add another item to the list.
cart = (List<OrderItem>)Session["cart"];
for(int counter = cart.Count-1; counter >= 0; counter--)
{
if (cart[counter].productId == item.productId)
{
cart[counter].productQuantity += item.productQuantity;
}
else if (counter == 0)
{
cart.Add(item);
}
}
cart[counter] and item represent an instance(s) of a custom object of mine. Currently when I finally find a matching ID, everything APPEARS as though it should work, but I get a StackOverflowException thrown in my custom object class.
public int productQuantity
{
get
{
return _productQuantity;
}
set
{
productQuantity = value;
}
}
It gets thrown right at the open-bracket of the "set". Could somebody please tell me what the heck is wrong because I've been going at this for the past 2+ hours to no avail. Thank you in advance.
the problem is in your setter of the productQuantity
it should read:
set
{
_productQuantity= value;
}
edit (naming convention):
public class Vertex3d
{
//fields are all declared private, which is a good practice in general
private int _x;
//The properties are declared public, but could also be private, protected, or protected internal, as desired.
public int X
{
get { return _x; }
set { _x = value; }
}
}
Replace productQuantity = value; with _productQuantity = value; (you're recurring infinitely by calling the setter over and over)
Why not just use this instead?
public int productQuantity { get; set; }
But the flaw was in the _
public int productQuantity {
get {
return _productQuantity;
}
set {
_productQuantity = value;
}
}
cart = (List<OrderItem>)Session["cart"];
int index = cart.Find(OrderItem => OrderItem.productId == item.productId);
if(index == -1) {
cart.Add(item);
} else {
cart[index].productQuantity += item.productQuantity;
}
public int productQuantity
{
get
{
return _productQuantity;
}
set
{
_productQuantity = value; //this should be an assignment to a member variable.
}
}

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