完整的极简（非工作）代码：http://pastebin.com/GPdSxyrt

我正在尝试PInvoke GetVirtualDiskInformation（https://msdn.microsoft.com/en-us/library/windows/desktop/dd323670(v=vs.85).aspx），并将代码设置为：

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct GetVirtualDiskInfo
{
    public GetVirtualDiskInfoVersion Version; //GET_VIRTUAL_DISK_INFO_VERSION
    public GetVirtualDiskInfoUnion Union;
}

[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode)]
public struct GetVirtualDiskInfoUnion
{
    [FieldOffset(0)] public GetVirtualDiskInfoSize Size;
    [FieldOffset(0)] public Guid Identifier; //GUID
    [FieldOffset(0)] public GetVirtualDiskInfoParentLocation ParentLocation;
    [FieldOffset(0)] public Guid ParentIdentifier; //GUID
    [FieldOffset(0)] public uint ParentTimestamp; //ULONG
    [FieldOffset(0)] public VirtualStorageType VirtualStorageType; //VIRTUAL_STORAGE_TYPE
    [FieldOffset(0)] public uint ProviderSubtype; //ULONG
    [FieldOffset(0)] public bool Is4kAligned; //BOOL
    [FieldOffset(0)] public bool IsLoaded; //BOOL
    [FieldOffset(0)] public GetVirtualDiskInfoPhysicalDisk PhysicalDisk;
    [FieldOffset(0)] public uint VhdPhysicalSectorSize; //ULONG
    [FieldOffset(0)] public ulong SmallestSafeVirtualSize; //ULONGLONG
    [FieldOffset(0)] public uint FragmentationPercentage; //ULONG
    [FieldOffset(0)] public Guid VirtualDiskId; //GUID
    [FieldOffset(0)] public GetVirtualDiskInfoChangeTrackingState ChangeTrackingState;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct GetVirtualDiskInfoSize
{
    public ulong VirtualSize; //ULONGLONG
    public ulong PhysicalSize; //ULONGLONG
    public uint BlockSize; //ULONG
    public uint SectorSize; //ULONG
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct GetVirtualDiskInfoParentLocation
{
    public bool ParentResolved; //BOOL
    public char ParentLocationBuffer; //WCHAR[1] //TODO
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct GetVirtualDiskInfoPhysicalDisk
{
    public uint LogicalSectorSize; //ULONG
    public uint PhysicalSectorSize; //ULONG
    public bool IsRemote; //BOOL
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct GetVirtualDiskInfoChangeTrackingState
{
    public bool Enabled; //BOOL
    public bool NewerChanges; //BOOL
    public char MostRecentId; //WCHAR[1] //TODO
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct VirtualStorageType
{
    public VirtualStorageDeviceType DeviceId; //ULONG
    public Guid VendorId; //GUID
}

public enum GetVirtualDiskInfoVersion
{
    Unspecified = 0,
    Size = 1,
    Identifier = 2,
    ParentLocation = 3,
    ParentIdentifier = 4,
    ParentTimestamp = 5,
    VirtualStorageType = 6,
    ProviderSubtype = 7,
    Is4KAligned = 8,
    PhysicalDisk = 9,
    VhdPhysicalSectorSize = 10,
    SmallestSafeVirtualSize = 11,
    Fragmentation = 12,
    IsLoaded = 13,
    VirtualDiskId = 14,
    ChangeTrackingState = 15
}

public enum VirtualStorageDeviceType
{
    Unknown = 0,
    Iso = 1,
    Vhd = 2,
    Vhdx = 3,
    Vhdset = 4
}

[DllImport("virtdisk.dll", CharSet = CharSet.Unicode)]
public static extern uint GetVirtualDiskInformation
(
    [In]            VirtualDiskSafeHandle virtualDiskHandle,
    [In, Out]   ref uint virtualDiskInfoSize,
    [In, Out]   ref GetVirtualDiskInfo virtualDiskInfo,
    [In, Out]   ref uint sizeUsed
);

我调用GetVirtualDiskInformation，如下所示：

var info = new GetVirtualDiskInfo {Version = infoVersion};
infoSize = (uint) Marshal.SizeOf(info);
var result = NativeMethods.GetVirtualDiskInformation(handle, ref infoSize, ref info, ref sizeUsed);

显然，handle在这里确实包含有效的VirtualDiskSafeHandle。
问题是我的out结构体完全搞砸了，数据到处都是，根据它，VHD的LogicalSectorSize是257，例如，它有一个负的VirtualSize。
我做错了什么？怎样才能让它正常工作？

编辑：

以下是一个具体的错误例子：
我创建了一个全新的VHDX作为差分（无父，无源），设置它的最大大小为50MB，LogicalSectorSize为512，PhysicalSectorSize为4096，BlockSize为2MB，它的VendorId（GUID）为new Guid("EC984AEC-A0F9-47e9-901F-71415A66345B")。
我希望在表演时：

var info = new GetVirtualDiskInfo {Version = GetVirtualDiskInfoVersion.Size};
infoSize = (uint) Marshal.SizeOf(info);
var result = NativeMethods.GetVirtualDiskInformation(handle, ref infoSize, ref info, ref sizeUsed);

info.Union.Size将返回：

VirtualSize = 52428800
PhysicalSize = 4194304
BlockSize = 2097152
SectorSize = 512

我得到的结果是“足够接近”。除了VirtualSize返回52428801之外，所有值都是正确的。现在，多出的一个字节可能是预期的，但我对此表示怀疑。不管怎样，接下来的两个示例产生了更糟糕的结果：

var info = new GetVirtualDiskInfo {Version = GetVirtualDiskInfoVersion.VirtualStorageType};
infoSize = (uint) Marshal.SizeOf(info);
var result = NativeMethods.GetVirtualDiskInformation(handle, ref infoSize, ref info, ref sizeUsed);

info.Union.VirtualStorageType的预期结果：

DeviceId = 2 //2 Symbolizes VHDX, which is how I created it
VendorId = "EC984AEC-A0F9-47e9-901F-71415A66345B" //As a GUID

实际结果：

DeviceId = 257
VendorId = "EC984AEC-A0F9-47e9-901F-71415A66345B" //As a GUID

换句话说，GUID是好的，DeviceId不是。257甚至不是一个有效值。
最后一个例子：

var info = new GetVirtualDiskInfo {Version = GetVirtualDiskInfoVersion.PhysicalDisk};
infoSize = (uint) Marshal.SizeOf(info);
var result = NativeMethods.GetVirtualDiskInformation(handle, ref infoSize, ref info, ref sizeUsed);

应返回info.Union.PhysicalDisk：

LogicalSectorSize = 512
PhysicalSectorSize = 4096
IsRemote = false

实际结果：

LogicalSectorSize  = 257
PhysicalSectorSize = 512
IsRemote = false

所以第一个值又是完全错误的，257不是一个可接受的值，第二个值也是错误的，我认为是4096。

EDIT2已将虚拟存储设备类型添加到初始代码中。
EDIT3完整示例如下：http://pastebin.com/GPdSxyrt
编辑4

我发现问题出在C语言中的WCHAR[1]字段上，如果我注解掉结构体GetVirtualDiskInfoUnion中的ChangeTrackingState，那么一切都很好。
尽管如此，我还是不确定在C#中如何设置它们，从我尝试的Angular 来看，它们似乎既不是char，也不是IntPtr，那么这到底意味着什么呢？