PInvoke的CreateDesktop

问题描述

我想的PInvoke CreateDesktop在传递标志继承桌面由子进程的方式。声明如下：

I am trying to PInvoke CreateDesktop in a way that passes the flag to inherit the desktop by child processes. The declaration is as follows:

[DllImport("user32", EntryPoint = "CreateDesktopW", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr CreateDesktop(string lpszDesktop, IntPtr lpszDevice, IntPtr pDevmode, int dwFlags,
                                                  int dwDesiredAccess, [MarshalAs(UnmanagedType.LPStruct)] SECURITY_ATTRIBUTES lpsa);

        [StructLayout(LayoutKind.Sequential)]
        public struct SECURITY_ATTRIBUTES
        {
            public int nLength;
            public IntPtr lpSecurityDescriptor;
            public int bInheritHandle;
        }

和我用它如下：

Win32.SECURITY_ATTRIBUTES sa = new Win32.SECURITY_ATTRIBUTES();
            sa.nLength = Marshal.SizeOf(sa);
            sa.bInheritHandle = 1;
            testDesktopHandle = Win32.CreateDesktop(name, IntPtr.Zero, IntPtr.Zero, 0, Win32.GENERIC_ALL, sa);

和它遗憾的是不工作，我得到以下错误：

And it unfortunately doesn't work, I get the following error:

System.Runtime.InteropServices.MarshalDirectiveException: Cannot marshal 'parameter #6': Invalid managed/unmanaged type combination (this value type must be paired with Struct).

任何想法我做错了吗？

Any ideas what I am doing wrong?

推荐答案

试着改变参数＃6〜

static extern IntPtr CreateDesktop(..., [In] ref SECURITY_ATTRIBUTES lpsa);

（此编译并不会抛出异常在运行时，但我只用伪造的参数进行了测试。）的

与 CreateDesktop C ++的声明比较

Compare with C++ declaration of CreateDesktop:

HDESK WINAPI CreateDesktop(..., __in_opt LPSECURITY_ATTRIBUTES lpsa);
                                  ↑      ↑ ↑
                                  [In] ref SECURITY_ATTRIBUTES lpsa

LP 代表长指针，即 LPSECURITY_ATTRIBUTES 是指向一个 SECURITY_ATTRIBUTES 结构。因此，在C＃中，你需要按引用传递的结构实例（价值型）。

LP stands for "long pointer", i.e. LPSECURITY_ATTRIBUTES is a pointer to a SECURITY_ATTRIBUTES struct. So in C# you need to pass your struct instance (value type) by reference.

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