小编BAR*_*ART的帖子

MutableSlab和ImmutableSlab实现之间的唯一区别是readonly应用于handle字段的修饰符：

using System;
using System.Runtime.InteropServices;

public class Program
{
    class MutableSlab : IDisposable
    {
        private GCHandle handle;

        public MutableSlab()
        {
            this.handle = GCHandle.Alloc(new byte[256], GCHandleType.Pinned);
        }

        public bool IsAllocated => this.handle.IsAllocated;

        public void Dispose()
        {
            this.handle.Free();
        }
    }

    class ImmutableSlab : IDisposable
    {
        private readonly GCHandle handle;

        public ImmutableSlab()
        {
            this.handle = GCHandle.Alloc(new byte[256], GCHandleType.Pinned);
        }

        public bool IsAllocated => this.handle.IsAllocated;

        public void Dispose()
        {
            this.handle.Free();
        }
    }

    public static void Main()
    { …

以下代码:

class B
{
    public bool FinishedDownloading { get; set; } = false;
};

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

A a = new A();

Console.WriteLine(a.DownloadStream?.FinishedDownloading != false);
Console.WriteLine(a.DownloadStream?.FinishedDownloading == true);

输出:

True
False

如何在地球上a.DownloadStream?.FinishedDownloading != false的true时候DownloadStream是null和FinishedDownloading是false？!

让我们忘记发生的事情并关注结果.

我们知道这种说法a.DownloadStream?.FinishedDownloading != false是正确的,因为它不是false,所以在我们的宇宙中,当某些东西是真的那么它应该是真的,因为1 == 1,对吧？

那么为什么当我们做a.DownloadStream?.FinishedDownloading == true结果时现在是假的？!疯狂.

我想我知道这里发生了什么.这是因为当DownloadStream null然后FinishedDownloading布尔值无法访问时,因此左侧为空,所以C#"认为":

• a.DownloadStream?.FinishedDownloading != false

  好的,让我们检查一下null值是否等于boolean"false"值.嗯,肯定没有,所以让我们输出真实.

• a.DownloadStream?.FinishedDownloading == …