是IntPtr.Zero相当于空？

问题描述

我试图安装的ReadFile 异步根据的，我需要设置 lpNumberOfBytesRead 到空：

I am trying to setup ReadFile to run asynchronously and according to MSDN, I need to set lpNumberOfBytesRead to null:

对，如果这是一个异步操作，以避免潜在的错误结果这个参数使用NULL。

例如，如果我有以下几点：

For example, if I have the following:

  [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
  public static extern bool ReadFile(
     IntPtr hFile,
     out byte[] aBuffer,
     int cbToRead,
     IntPtr cbThatWereRead,
     ref OVERLAPPED pOverlapped
  );

和我这样称呼它（与具有4个参数是空的意图）：

and I call it like this (with the intention of having the 4th parameter being null):

Win32API.ReadFile(readHandle, out data_read, Win32API.BUFFER_SIZE, IntPtr.Zero, ref over_lapped);

那将是一样的使用NULL调用？如果不是这样，我应该在报关或功能改变自称？

will that be the same as calling it with null? If not, what should I change in the declaration or in the function call itself?

我也好奇，如果我应该使用的SafeHandle 或 HandleRef 而不是的IntPtr 为 HFILE 引用？我知道，以确保我关闭与 CloseHandle的（IntPtr的）把手当我用它做的，只是不知道是否有任何行吟诗人理由使用其他两个在 IntPtr的选项。我也tryingn避免使用不安全的code。

I was also curious if I should be using SafeHandle or HandleRef instead of IntPtr for the hFile reference? I know to make sure that I close the handle with CloseHandle(IntPtr) when I'm done with it, just not sure if there is any othe reason to use the other two options over IntPtr. I am also tryingn to avoid using unsafe code.

编辑：事实证明，我不应该是第四个参数设置为 IntPtr.Zero ，无论如何，因为即使我异步运行，它仍然可以立即返回。请参见。啊，我喜欢矛盾的故事。

As it turns out, I shouldnt be setting the fourth parameter to IntPtr.Zero anyway, because even though I am running asynchronously, it could still return right away. See Asynchronous Disk I/O. Ahh, I love contradicting stories.

推荐答案

有关的P / Invoke的目的，就像你上市，你应该代替使用 IntPtr.Zero NULL 。请注意，这并不等同于C＃空关键字，但是。

For P/Invoke purposes like you've listed, you should use IntPtr.Zero in place of NULL. Note that this is not equivalent to the C# null keyword, however.

这篇关于是IntPtr.Zero相当于空？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！