C# 学习笔记 参数使用
Windows 7 没有装 visual studio 有些参数修饰符不兼容Microsoft (R) Visual C# Compiler version 4.8.3761.0
for C# 5
Copyright (C) Microsoft Corporation. All rights reserved.
This compiler is provided as part of the Microsoft (R) .NET Framework, but only supports language versions up to C# 5, which is no longer the latest version. For compilers that support newer versions of the C# programming language, see http://go.microsoft.com/fwlink/?LinkID=533240
装了frameWork4.8 提示我这是5.0版本！必须安装 visual studio 才能升级C# 版本吗？
using System;
class Method
{
static void Main()
{
// int x = 101;
// ValueTransfer(x);
// x = 101, GetHashCode = 101
// Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
// Student stu = new Student(){name = "Tim"};
// x = Tim, GetHashCode = 46104728
// Console.WriteLine("x = {0}, GetHashCode = {1}", stu.name, stu.GetHashCode());
// ValueQuote(stu);
// x = Tom, GetHashCode = 46104728
// Console.WriteLine("x = {0}, GetHashCode = {1}", stu.name, stu.GetHashCode());
// int x = 100;
// x = 100, GetHashCode = 100
// Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
// ValueQuoteRef(ref x);
// x = 1, GetHashCode = 1
// Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
// double x = default(double);
// x = 0, GetHashCode = 0
// Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
// ValueQuoteOut(out x);
// x = 100, GetHashCode = 100
// Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
// Borrow stu = new Borrow();
// stu.ShowBook();
// Book book = new Book();
// book.title = "C#";
// 查询书籍名
// if (stu.Query(ref book))
// {
// book.borrow = "A, B, C, GIN";
// Console.WriteLine("----------更改分割线----------");
// }
// else
// {
// Console.WriteLine("--------未更改分割线----------");
// }
// stu.ShowBook();
// 不定长参数
// Parameters(1,2,3,4,1,5,5);
double pi = 3.14159666;
// pi就是this修饰的那个参数
double rpi = pi.Round(3);
// 3.14159666 保留 3 位小数后为 3.142
Console.WriteLine("{0} 保留 {1} 位小数后为 {2}", pi, 3, rpi);
}
class Student
{
public string name {get; set;}
}
class Book
{
public string title{get;set;}
public string borrow{get;set;}
}
class Borrow
{
// books 存放着每本书的借用着
Book[] books =
{
new Book(){title = "C#", borrow="A"},
new Book(){title = "C", borrow="A"},
new Book(){title = "Python", borrow="A, B"}
};
// ref 一个引用实例
// Book temp = null;
// public ref Book Query(string title)
// {
// for (int i = 0; i < books.Length; i++)
// {
// if (title = books.title)
// {
// return ref title;
// }
// }
// return ref temp;
// }
// Book temp = null;
// 存储一个book地址的信息抛出去，使外部也能更改
public bool Query(ref Book book)
{
for (int i = 0; i < books.Length; i++)
{
if (book.title == books.title)
{
book = books;
return true;
}
}
return false;
}
// 输出books信息
public void ShowBook()
{
for (int i = 0; i < books.Length; i++)
{
Console.WriteLine("{0,-10} by {1}", books.title, books.borrow);
}
}
}
// 传值
static void ValueTransfer(int x)
{
x = 100;
// x = 100, GetHashCode = 100
Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
}
// 引用一个自生就是引用类型的值
static void ValueQuote(Student stu)
{
// 可以这样理解
// 创建一个Student stu 然后将外面的stu 复制给内部的stu， stu（内） = stu（外）
// 引用的目标地址相同
stu.name = "Tom";
// x = Tom, GetHashCode = 46104728
Console.WriteLine("x = {0}, GetHashCode = {1}", stu.name, stu.GetHashCode());
}
// ref 参数修饰符 引用传值，[（in 参数修饰符）方法内只读 ]
static void ValueQuoteRef(ref int x)
{
x = 1;
// x = 1, GetHashCode = 1
Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
}
// out 参数修饰符，方法内部必须对参数至少修改一次
static void ValueQuoteOut(out double x)
{
try
{
x = Double.Parse(Console.ReadLine());
}
catch
{
x = 6;
}
// x = <input>, GetHashCode = <input>
Console.WriteLine("x = {0}, GetHashCode = {1}", x, x.GetHashCode());
}
static void Parameters(params int[] array)
{
// foreach (var a in array)
// {
// Console.WriteLine(a);
// }
// array = 1
// array = 2
// array = 3
// array = 4
// array = 1
// array = 5
// array = 5
for (int i = 0; i < array.Length; i++)
{
Console.WriteLine("array[{0}] = {1}", i, array);
}
}
}
// 类扩展方法
// 扩展方法必须在顶级静态类中定义
public static class DoubleExtension
{
// 必须是静态的。第一个参数必须使用 this 修饰符
public static double Round(this double a, int digital)
{
return Math.Round(a, digital);
}
} 学习大佬啊，不用安装也可以 lili2312280 发表于 2021-3-2 11:24
学习大佬啊，不用安装也可以
看完一节课，总结一下。我去查查怎么升级！ VS2019社区版本，用.net core吧 Alex.Merceryj 发表于 2021-3-2 12:25
VS2019社区版本，用.net core吧
.net core兼容性更好吗？ Cool_Breeze 发表于 2021-3-2 12:44
.net core兼容性更好吗？
跨平台的，大趋势。这个c#语言都是通用的，环境比较好
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