jeb's questions

我不明白为什么这段代码会抛出 nullref。我认为这与“加”运算符和“是”运算符的优先级有关，但我真的不确定为什么。

 return "somestring " + B is not null  ? $" {B.Property}" : "empty";

完整样本：

internal class Program
 {
     static void Main(string[] args)
     {
         var a = new A();
         Console.WriteLine(a.ToString());
         Console.ReadKey();
     }
 }

 public class A
 {
     public B? B  { get; set; }

     public override string ToString()
     {
         return "somestring " + B is not null  ? $" {B.Property}" : "empty"; //nullref 
         return "somestring " + (B is not null ? $" {B.Property}" : "empty"); //works
     }
 }

 public class B
 {
     public string Property { get; set; } = "Property";
 }

作用域服务方法内的信号量是否一次只允许一个人访问？

public class MyScopedService
{
    private readonly SemaphoreSlim semaphore = new SemaphoreSlim(1, 1); 

    public async Task SomeMethod()
    {
        await semaphore.WaitAsync();
        try
        {
            // Access the shared resource here
        }
        finally
        {
            semaphore.Release();
        }
    }
}

在 DI 中注册：

 services.AddScoped<MyScopedService>();