// 不優(yōu)化的情況：每次都創(chuàng)建新的 StringBuilder
for (int i = 0; i < 1000; i++)
{
    var builder = new StringBuilder();
    builder.Append("Number: ");
    builder.Append(i);
    Console.WriteLine(builder.ToString());
}

// 優(yōu)化后的情況：重用同一個(gè) StringBuilder
var sharedBuilder = new StringBuilder();
for (int i = 0; i < 1000; i++)
{
    sharedBuilder.Clear();
    sharedBuilder.Append("Number: ");
    sharedBuilder.Append(i);
    Console.WriteLine(sharedBuilder.ToString());
}

// 使用 List<T>
List<int> numbersList = new List<int> { 1, 2, 3, 4, 5 };

// 使用 Array
int[] numbersArray = new int[] { 1, 2, 3, 4, 5 };

// 當(dāng)數(shù)據(jù)量固定時(shí)，Array 比 List<T> 更節(jié)省內(nèi)存

Dictionary<int, string> employeeDirectory = new Dictionary<int, string>();

employeeDirectory[1002] = "Robert";

//快速查找更新，字典更快捷

// 使用 class
class PointClass
{
    public int X { get; set; }
    public int Y { get; set; }
}
// 使用 struct
struct PointStruct
{
    public int X { get; set; }
    public int Y { get; set; }
}

// struct 通常會(huì)節(jié)省內(nèi)存，尤其是在大量小對(duì)象的情況下
// 使用 class
void ProcessPointsClass()
{
    for (int i = 0; i < 1000000; i++)
    {
        PointClass p1 = new PointClass(i, i);
    }
}
// 使用 struct
void ProcessPointsStruct()
{
    for (int i = 0; i < 1000000; i++)
    {
        PointStruct p1 = new PointStruct(i, i);
    }
}

using System;
using System.Collections;
class Program
{
    static void Main()
    {
        ArrayList list = new ArrayList();
        
        // 裝箱：整數(shù)被包裝成對(duì)象
        list.Add(42);
        
        // 拆箱：對(duì)象被轉(zhuǎn)換回整數(shù)
        int value = (int)list[0];
        
        Console.WriteLine($"Value: {value}");
    }
}


using System;
using System.Collections.Generic;
class Program
{
    static void Main()
    {
        List<int> list = new List<int>();
        
        // 不需要裝箱：整數(shù)直接存儲(chǔ)為值類型
        list.Add(42);
        
        // 不需要拆箱：整數(shù)直接檢索為值類型
        int value = list[0];
        
        Console.WriteLine($"Value: {value}");
    }
}

// 不使用 StringBuilder
string result = "";
for (int i = 0; i < 100; i++)
{
    result += i.ToString(); // 創(chuàng)建多個(gè)中間字符串對(duì)象
}

// 使用 StringBuilder
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 100; i++)
{
    sb.Append(i.ToString());
}
string optimizedResult = sb.ToString(); // 更高效

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "example.txt";

        // 使用 using 語(yǔ)句確保文件在讀取后正確關(guān)閉
        using (StreamReader reader = new StreamReader(filePath))
        {
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                Console.WriteLine(line);
            }
        } // 離開(kāi) using 塊時(shí)，reader 對(duì)象的 Dispose 方法被自動(dòng)調(diào)用

        Console.WriteLine("文件讀取完畢，資源已釋放。");
    }
}

using System;
using System.Collections.Generic;
using System.Drawing;

class Program
{
    // 使用字典來(lái)存儲(chǔ)圖像的弱引用緩存
    static Dictionary<string, WeakReference> imageCache = new Dictionary<string, WeakReference>();

    static void Main()
    {
        string imagePath = "example.png";
        Bitmap image = LoadImage(imagePath);

        if (image != null)
        {
            Console.WriteLine("圖像已加載并緩存。");
        }
        else
        {
            Console.WriteLine("圖像加載失敗。");
        }

        // 強(qiáng)制垃圾回收以演示弱引用效果
        GC.Collect();
        GC.WaitForPendingFinalizers();
        
        // 再次嘗試從緩存加載圖像
        image = LoadImage(imagePath);
        if (image != null)
        {
            Console.WriteLine("圖像已從緩存中重新加載。");
        }
        else
        {
            Console.WriteLine("圖像已被垃圾回收器回收。");
        }
    }

    static Bitmap LoadImage(string path)
    {
        if (imageCache.TryGetValue(path, out WeakReference weakRef) && weakRef.IsAlive)
        {
            Console.WriteLine("從緩存中獲取圖像...");
            return weakRef.Target as Bitmap;
        }
        else
        {
            Console.WriteLine("加載新圖像...");
            Bitmap img = new Bitmap(path);

            // 將圖像加載到緩存中
            imageCache[path] = new WeakReference(img);
            return img;
        }
    }
}