vc的结构问题

[dsd999]

typedef struct _SP_DEVINFO_DATA {
DWORD cbSize;
GUID ClassGuid;
DWORD DevInst;
ULONG_PTR Reserved;
} SP_DEVINFO_DATA, *PSP_DEVINFO_DATA;
在vc中sizeof取得结构的大小是28。

转换到c#中
[StructLayout(LayoutKind.Sequential)]
public class SP_DEVINFO_DATA
{
public UInt32 cbSize;
public Guid ClassGuid;
public UInt32 DevInst;
public ulong Reserved;
};
SP_DEVINFO_DATA spData = new SP_DEVINFO_DATA();
spData.cbSize = (UInt32)System.Runtime.InteropServices.Marshal.SizeOf(spData);

大小为什么变成了32？

[best8625]

up

[王集鹄]

C#中long是64位也就是8个字节
ULONG_PTR是4个字节
所以上面的结构多了4个字节
32-4=28

[StructLayout(LayoutKind.Sequential)]
public class SP_DEVINFO_DATA
{
public UInt32 cbSize;
public Guid ClassGuid;
public UInt32 DevInst;
public IntPtr Reserved; //<<<<<<<
};

[xiaoliangwh]

up

[dsd999]

SP_DEVINFO_DATA spData = new SP_DEVINFO_DATA();
spData.cbSize = (UInt32)System.Runtime.InteropServices.Marshal.SizeOf(spData);

NewDeviceInfoSet = SetupDiGetClassDevs(0, "PCI", IntPtr.Zero, DIGCF_PRESENT | DIGCF_ALLCLASSES);

SetupDiEnumDeviceInfo(NewDeviceInfoSet, RequiredSize, ref spData);

为什么这条语句执行没有成功？？GetLastError返回ERROR_INVALID_USER_BUFFER，为什么，哪用错了吗？

[Knight94]

ref:
http://www.pinvoke.net/default.aspx/setupapi/SetupDiEnumDeviceInfo.html