浅谈熟悉C#如何转TypeScript

// C#
string name = "Alice";
int age = 30;
var isActive = true; // 类型推断

// TypeScript
const name: string = "Alice";
let age: number = 30;
const isActive = true; // 类型自动推断为 boolean

// C#
public int Add(int a, int b)
{
    return a + b;
}

// 或表达式体
public int Multiply(int a, int b) => a * b;

// TypeScript
function add(a: number, b: number): number {
    return a + b;
}
// 或箭头函数（更常见）
const multiply = (a: number, b: number): number => a * b;
// 返回类型通常可省略（TS 能推断）
const subtract = (a: number, b: number) => a - b;

// C#
public class Animal
{
    public string Name { get; set; }
    
    public Animal(string name) => Name = name;
    
    public virtual void Speak() => Console.WriteLine("...");
}

public class Dog : Animal
{
    public Dog(string name) : base(name) { }
    
    public override void Speak() => Console.WriteLine("Woof!");
}

// TypeScript
class Animal {
    constructor(public name: string) {} // 自动创建并赋值 this.name
    speak(): void {
        console.log("...");
    }
}
class Dog extends Animal {
    speak(): void {
        console.log("Woof!");
    }
}

// C#
public interface IPerson
{
    string Name { get; set; }
    int Age { get; }
    void Greet();
}

// TypeScript
interface Person {
    name: string;
    readonly age: number; // 只读 ≈ C# 的 { get; }
    greet(): void;
}

const person: Person = { name: "Bob", age: 25, greet() { console.log("Hi"); } };

// C#
public class Box<T>
{
    public T Value { get; set; }
    
    public Box(T value) => Value = value;
}

var numberBox = new Box<int>(42);

// TypeScript
class Box<T> {
    constructor(public value: T) {}
}
const numberBox = new Box<number>(42);
// 或让 TS 推断
const stringBox = new Box("hello");

// C#
public async Task<string> FetchDataAsync()
{
    using var client = new HttpClient();
    return await client.GetStringAsync("https://api.example.com/data");
}

// TypeScript（浏览器或 Node.js 环境）
async function fetchData(): Promise<string> {
    const response = await fetch("https://api.example.com/data");
    return await response.text();
}
// 或使用 axios（需安装）
import axios from 'axios';
async function fetchData2(): Promise<string> {
    const res = await axios.get<string>("https://api.example.com/data");
    return res.data;
}

// C#
string? maybeName = GetName(); // 可空引用类型（C# 8+）
if (maybeName != null)
    Console.WriteLine(maybeName.Length);

// TypeScript（tsconfig.json 中开启 "strictNullChecks": true）
function getName(): string | null {
    return Math.random() > 0.5 ? "Alice" : null;
}
const maybeName = getName();
if (maybeName !== null) {
    console.log(maybeName.length); // 安全访问
}