C#中的CS0649错误 [英] CS0649 error in C#
问题描述
代码中有一个我找不到的错误，有些变量根本无法工作.
There's a bug in the code somewhere that I can't find, some variables simply don't work somehow.
我得到的警告:
CS0649字段"Calculations.A"从未分配，并且其默认值始终为0 ABC-Formule [path] \ Calculations.cs
CS0649 Field 'Calculations.A' is never assigned to, and will always have its default value 0 ABC-Formule [path]\Calculations.cs
CS0649字段"Calculations.B"从未分配，并且其默认值始终为0 ABC-Formule [path] \ Calculations.cs
CS0649 Field 'Calculations.B' is never assigned to, and will always have its default value 0 ABC-Formule [path]\Calculations.cs
CS0649字段"Calculations.C"从未分配，并且其默认值始终为0 ABC-Formule [path] \ Calculations.cs
CS0649 Field 'Calculations.C' is never assigned to, and will always have its default value 0 ABC-Formule [path]\Calculations.cs
代码:Program.cs
Code: Program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ABC_Formule
{
class Program
{
static void Main(string[] args)
{
bool keepGoing = true;
while (keepGoing)
{
//Definieren strings gebruikt in Main
string a;
string b;
string c;
string keepGoingString;
string discriminantString;
double aDouble;
double bDouble;
double cDouble;
double discriminantValue;
double singleX;
double doubleX1;
double doubleX2;
//Vraag de user om input
Console.WriteLine("Welkom bij de ABC-Calculator. Gemaakt door Luciano Nooijen.");
Console.WriteLine("Zorg voor een correcte invoer. De opbouw van een formule is ax^2 + bx + c.");
Console.WriteLine("");
Console.WriteLine("Vul de juiste variabelen in: (komma = ,)");
Console.Write("a: "); a = Console.ReadLine();
Console.Write("b: "); b = Console.ReadLine();
Console.Write("b: "); c = Console.ReadLine();
//Omzetten van string naar double
aDouble = Convert.ToDouble(a);
bDouble = Convert.ToDouble(b);
cDouble = Convert.ToDouble(c);
Console.WriteLine("a, b en c zijn: " + aDouble + ", " + bDouble + " en " + cDouble);
Console.WriteLine("");
//Invoeren getallen in berekenfunctie
Calculations berekeningen = new Calculations(aDouble, bDouble, cDouble);
//Discriminant berekenen
discriminantValue = berekeningen.Discriminant();
//Validatie discriminant en output
discriminantString = berekeningen.ValidDiscriminant();
if (discriminantString == "Gelijk") //Enkele output
{
singleX = berekeningen.OutputOnlyX();
Console.WriteLine("De discriminant is: " + discriminantValue);
Console.WriteLine("Het x-coördinaat is: " + singleX);
}
else if (discriminantString == "Groter") //Dubbele output
{
doubleX1 = berekeningen.OutputX1();
doubleX2= berekeningen.OutputX2();
Console.WriteLine("De discriminant is: " + discriminantValue);
Console.WriteLine("Het x1-coördinaat is: " + doubleX1);
Console.WriteLine("Het x2-coördinaat is: " + doubleX2);
}
else if (discriminantString == "Kleiner") //Geen snijpunt
{
Console.WriteLine("De discriminant is: " + discriminantValue + " en er is dus geen snijpunt met de x-as.");
}
else //Ongeldige invoer
{
Console.WriteLine("Ongeldige invoer");
}
//Vragen of gebruiker door wil gaan
Console.Write("Druk op enter om door te gaan, of druk op typ q om af te sluiten: "); keepGoingString = Console.ReadLine();
if (keepGoingString.Equals("q"))
{
keepGoing = false;
}
else
{
Console.WriteLine("");
Console.WriteLine("-----------------------------------------------------------");
Console.WriteLine("");
Console.Clear();
}
}
}
}
}
Calculations.cs
Calculations.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ABC_Formule
{
class Calculations
{
protected double A;
protected double B;
protected double C;
protected double DiscriminantValue;
public Calculations (double a, double b, double c)
{
double A = a;
double B = b;
double C = c;
}
public double Discriminant ()
{
DiscriminantValue = B*B-4*A*C;
return DiscriminantValue;
}
public string ValidDiscriminant()
{
if (DiscriminantValue < 0) //Geen uitkomst
{
return "Kleiner";
}
else if (DiscriminantValue == 0) //1 uitkomst
{
return "Gelijk";
}
else if (DiscriminantValue > 0) //Twee uitkomsten
{
return "Groter";
}
else //Bij fout
{
return "Error";
}
}
public double OutputOnlyX ()
{
return (-B + Math.Sqrt(DiscriminantValue) ) / (2 * A);
}
public double OutputX1 ()
{
return (-B - Math.Sqrt(DiscriminantValue)) / (2 * A);
}
public double OutputX2 ()
{
return (-B + Math.Sqrt(DiscriminantValue)) / (2 * A);
}
}
}
推荐答案
在 Calculations 构造函数中，您具有:
In Calculations constructor you have:
double A = a;
您想要的:
A = a; // or this.A = a;
代替(当然这也涉及 B 和 C ).
instead(this of course concerns also B and C).
在代码中，您将创建一个本地变量(在构造函数的范围内) A ，该变量与该类的 A 字段无关(除了令人困惑之外，，同名).在这种情况下发生的事情称为阴影，有效地导致了每个 A 在此函数的代码中表示局部变量，而不是父作用域中的字段.
In your code, you create a local (in the scope of the constructor) variable A that has nothing to do with the class's A field (beside having, confusingly, the same name). What happens in such a situation is called shadowing, effectively causing every A in this function's code to mean the local variable, not the field in the parent scope.
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