单例模式

public class Singleton
{private static Singleton instance = null;private static readonly object syncRoot = new object();private Singleton() { }public static Singleton Instance{get{if (instance == null){lock (syncRoot){if (instance == null){instance = new Singleton();}}}return instance;}}
}

这个实现使用了双重检查锁定（double-checked locking），以确保在多线程环境下也能高效安全地创建单例。首次检查instance == null是为了避免在单例已经被创建后的每次调用中都进行锁定，而内部的检查则确保了即使在多线程情况下只有一个实例被创建

代码优化

常规写法

FileStream? fs = null;
if (fs == null)fs = new FileStream("1.txt", FileMode.CreateNew, FileAccess.ReadWrite);

使用代码优化(复合分配)

FileStream? fs = null;
fs ??= new FileStream("1.txt", FileMode.CreateNew, FileAccess.ReadWrite);

内联变量声明

以前写法

Dictionary<string, string >  dic = new Dictionary<string, string>();string? content = null;
dic.TryGetValue("aaa", out  content);

内联写法

Dictionary<string, string >  dic = new Dictionary<string, string>();dic.TryGetValue("aaa", out string? content);