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POIs IntPtr.Zero equivalent to null?
 

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    <p>I am trying to setup <code>ReadFile</code> to run asynchronously and according to <a href="http://msdn.microsoft.com/en-us/library/aa365467(VS.85).aspx" rel="noreferrer">MSDN</a>, I need to set <code>lpNumberOfBytesRead</code> to <code>null</code>:</p> <blockquote> <p>"Use NULL for this parameter if this is an asynchronous operation to avoid potentially erroneous results."</p> </blockquote> <p>For example, if I have the following:</p> <pre><code> [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 ); </code></pre> <p>and I call it like this (with the intention of having the 4th parameter being null):</p> <pre><code>Win32API.ReadFile(readHandle, out data_read, Win32API.BUFFER_SIZE, IntPtr.Zero, ref over_lapped); </code></pre> <p>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?</p> <p>I was also curious if I should be using <code>SafeHandle</code> or <code>HandleRef</code> instead of <code>IntPtr</code> for the <code>hFile</code> reference? I know to make sure that I close the handle with <code>CloseHandle(IntPtr)</code> when I'm done with it, just not sure if there is any othe reason to use the other two options over <code>IntPtr</code>. I am also tryingn to avoid using unsafe code.</p> <p>EDIT: As it turns out, I shouldnt be setting the fourth parameter to <code>IntPtr.Zero</code> anyway, because even though I am running asynchronously, it could still return right away. See <a href="http://support.microsoft.com/kb/156932" rel="noreferrer">Asynchronous Disk I/O</a>. Ahh, I love contradicting stories.</p>
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