在简单的学校系统中，访问器和变量的以下问题的解决方法是什么? [英] What is the fix to the following problems with Accessors and Mutators in a simple school system?

问题描述

大家好，

我正在学习C#，现在我正在尝试通过开发一个简单的学校系统来练习所学的知识.我遇到了很多问题，我也不知道为什么.像这样编译它们时，我有很多错误:

错误11``SchoolSystem.Student.setGrade(int)''的最佳重载方法匹配具有一些无效参数


请帮我.

我的代码是:

Hello everybody,

I am learning C# and now I am trying to practice what I learned by developing a simple school system. I faced a lot of problems and I do not know why. I have a lot of errors when I compiled them like:

Error 11 The best overloaded method match for ''SchoolSystem.Student.setGrade(int)'' has some invalid arguments


Please help me.

My code is:

using System;

namespace SchoolSystem {

    public class Student {

        //Variables
        string name;
        string id;
        double grade;

        //Constructors
        public Student() : this("Default Constructor") { }

        public Student(string name)
        {

            this.Name = name;
        }

        public Student(string name, string id)
        {

            this.Name = name;
            this.Id = id;
        }

        public Student(string name, string id, double grade) {

            this.Name = name;
            this.Id = id;
            this.Grade = grade;
        }

        //Accessors
        public string getName(){
        
            return name;
        }

        public string getId(){
        
            return id;
        }

        public int getGrade()
        {
        
            return grade;
        }
        
        //Mutators
        public string setName(string newName){
        
            name = newName;
        }

        public string setId(string newId){
        
            id = newId;
        }

        public int setGrade(int newGrade){
        
            grade = newGrade;
        }

    }

    public class SchoolSystem{
    
        public static void Main(String [] args){

            Console.WriteLine("-----------------------------------");
            Console.WriteLine("Welcome to Dhahran Secondary School");
            Console.WriteLine("-----------------------------------");

            Student s1 = new Student();
            Console.WriteLine("Please enter the student name: ");
            s1.setName(Console.ReadLine());
            Console.WriteLine("Please enter the student id: ");
            s1.setId(Console.ReadLine());
            Console.WriteLine("Please enter the student grade: ");
            s1.setGrade(Console.ReadLine());

            Student s2 = new Student();
            Console.WriteLine("Please enter the student name: ");
            s2.setName(Console.ReadLine());
            Console.WriteLine("Please enter the student id: ");
            s2.setId(Console.ReadLine());
            Console.WriteLine("Please enter the student grade: ");
            s2.setGrade(Console.ReadLine());

            Student s3 = new Student();
            Console.WriteLine("Please enter the student name: ");
            s3.setName(Console.ReadLine());
            Console.WriteLine("Please enter the student id: ");
            s3.setId(Console.ReadLine());
            Console.WriteLine("Please enter the student grade: ");
            s3.setGrade(Console.ReadLine());

            Console.WriteLine("The System Information");
            Console.WriteLine("The information of: {0}", s1.getName(), "\nID: ", s1.getId(), "\nGrade: ", s1.getGrade());
            Console.WriteLine("The information of: {0}", s2.getName(), "\nID: ", s2.getId(), "\nGrade: ", s2.getGrade());
            Console.WriteLine("The information of: {0}", s3.getName(), "\nID: ", s3.getId(), "\nGrade: ", s3.getGrade());

            Console.ReadLine();
        } 
    }


}

推荐答案

很抱歉，我看到了一个未提出的问题的答案，所以我再给它一个镜头: )
问题是这些线

Sorry I see gave an answer to a question that wasn''t asked, so I''ll give it another shot :)
the problem is these lines

s1.setGrade(Console.ReadLine());
s2.setGrade(Console.ReadLine());
s3.setGrade(Console.ReadLine());

Console.ReadLine()返回一个字符串，但setGrade接受一个整数，您可以使用 Converter.ToInt32 [ ^ ]将字符串转换为整数，但如果不能，则会引发异常，因此您可能想使用 int.TryParse [ ^ ]例如:

Console.ReadLine() returns a string but setGrade accepts an integer you can use Converter.ToInt32[^] to convert a string to an integer, but it throws an exception if it cannot so you may want to use int.TryParse[^] eg.:

int i;
if(int.TryParse("100", out i))
{
    // the string is representing an integer, the integer is now in i
}
else
{
    // the string is NOT representing an integer, i is 0
}

这是原始的错误"答案，但是您可能仍然希望看到它.
好吧，它们本身没有问题.但是在C#中，我们更喜欢使用属性.
属性(C#编程指南)
[^ ]

因此，而不是

Here is the original "wrong" answer, but you may wnat to see it anyhow.
Well there is no problem with them per se. But in C# we like to use properties instead.
Properties (C# Programming Guide)
[^]

So instead of

 public string getName(){
    return name;
}
public string setName(string newName){    
    name = newName;
}

你可以写

you can write

public string Name
{
    get { return name; }
    set { name = value; }
}

甚至

or even

public string Name {get; set; }

如果您不使用字段name.编译器将为auto属性创建后备字段.

if you do not use the field name. The compiler will make the backing field for the auto property.

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