Question

我是C＃的新手，在我的教科书中它要求我在Program.cs类的main方法中添加一些代码，但是没有告诉我如何。我是一个初学者，所以我只是在寻找基础知识，当我出去的时候，我会接受更高级的课程，所以请保持你的解释彻底，但是一直到第一天。以下是我提供的代码。它不断向我提供错误＆lt;

下面的代码如下：我应该将公共静态语音TestIfElse方法添加到Program.cs类中：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ifelse_Statement
{
    class Program
    {
        static void Main(string[] args)
        {
            TestIfElse(10);
            public static void TestIfElse(int n)
            {
                if (n < 10)
                {
                    Console.WriteLine(“n is less than 10”);
                }
                else if (n < 20)
                {
                    Console.WriteLine(“n is less than 20”);
                }
                else if (n < 30)
                {
                    Console.WriteLine(“n is less than 30”);
                }
                else
                {
                    Console.WriteLine(“n is greater than or equal to 30”);
                }
            }
        }
    }
}

Answer 1

您的错误很简单 - 您无法在C＃中使用嵌套函数。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ifelse_Statement
{
    class Program
    {
        static void Main(string[] args)
        {
            TestIfElse(10);
        }
        public static void TestIfElse(int n)
        {
            if (n < 10)
            {
                Console.WriteLine(“n is less than 10”);
            }
            else if (n < 20)
            {
                Console.WriteLine(“n is less than 20”);
            }
            else if (n < 30)
            {
                Console.WriteLine(“n is less than 30”);
            }
            else
            {
                Console.WriteLine(“n is greater than or equal to 30”);
            }
        }
    }
}

Answer 2

您应该将TestIfElse方法的主体移出Main方法的主体。这样他们都被认为是班级的方法，并将按照需要工作。

此外，在您的逻辑中，您需要检查范围，即小于20的数字也小于30，因此您可能想要检查数字是否在10到20之间，或20到30之间，依此类推。

static void Main(string[] args)
    {
        TestIfElse(10);
    }

public static void TestIfElse(int n)
{
    if (n < 10)
    {
        Console.WriteLine(“n is less than 10”);
    }
    else if (n < 20)
    {
        Console.WriteLine(“n is less than 20”);
    }
    else if (n < 30)
    {
        Console.WriteLine(“n is less than 30”);
    }
    else
    {
        Console.WriteLine(“n is greater than or equal to 30”);
    }
}

Answer 3

ClassHere是类

的基本结构

public class MyClass // this is the declaration of the class 
{
    // this is a property, it is accessible by things outside of this class.
    public static string MyProperty { get; set; } ;
    private static string _myField; // this is a ['private] field, it is intended to store the state of the object. it cannot be accessed from outside of this class

    static void Main(string[] args)
    {
        // this is the method that gets run first so it make all of your initial calls
    }

    public static void TestIfElse(int n)
    {
        // this is another method (taught as module, operation, action, or subroutine in schools)
        // it has return type of void which is more or less "nothing". This type of behavior simply does 
        // something but doesn't return a value
    }

    public static bool IsNotPrime(int input)
    {
        // this is an actual function in that will return a single value whether its a primitive value or an
        // object. Whatever it is, there's ONE. The point is that a call to this function is now synonymous with
        // the value it returns. So for example, if this method was real, it is equivalent to 'true' so you could 
        // actually say if(IsNotPrime(8)){ // do things }
        return input % 2 == 0;
    }
}

你必须将这些方法分开。类可以有很多成员（字段，属性，方法等），一个方法可以调用另一个，但是方法不能包含另一个。因此，当您学习识别这些时，如果您看到诸如public或static之类的关键字，您应该认为这些必须是类内部的实体，而不是其他类成员之外的实体。

例如，除了类声明本身之外，private或private static（或任何其他访问修饰符）在类型和标识符之前是您在声明类方法时看到的第一件事，所以不要试图在该成员中加入其他任何东西。

您使用代码时遇到的问题主要是TestIfElse的声明。你已经在main函数内部声明了它，你不能这样做。将它移到main之外，你应该没问题。

理解C＃代码机制

3 个答案: