调用OpenVirtualDisk()返回错误码2“文件未找到”的技术求助

刚从Borland Pascal转C#，正在做一个基于Windows Imaging API的恢复套件，要在WinPE（Windows 10 + .NET 5.4.2）环境里挂载ISO文件，结果调用OpenVirtualDisk()的时候一直翻车——明明文件存在，程序也以管理员权限运行，要么返回错误码87（无效参数，GetLastWin32Error返回1008“无效令牌”），要么返回错误码2（文件未找到）。试了FileIOPermission给全权限也没用，差点头大。

先贴下我一开始的错误代码：

原DllImport声明 #

[DllImport("VirtDisk.dll", EntryPoint = "OpenVirtualDisk", CharSet = CharSet.Ansi, ThrowOnUnmappableChar = true ,SetLastError = true)]
public extern static Int64 OpenVirtualDisk(
[In] ref _VIRTUAL_STORAGE_TYPE PVIRTUAL_STORAGE_TYPE,
string Path,
_VIRTUAL_DISK_ACCESS_MASK LVIRTUAL_DISK_ACCESS_MASK,
long OPEN_VIRTUAL_DISK_FLAG,
[In, Optional] ref OPEN_VIRTUAL_DISK_PARAMTERS POPEN_VIRTUAL_DISK_PARAMTERS,
ref IntPtr pHandle);

原调用逻辑 #

private void button1_Click(object sender, EventArgs e) {
    IntPtr pHandle = IntPtr.Zero;
    Int64 RetVal = 0;
    string VirtualDiskPath = @"F:\Images\Windows10.ISO";
    _VIRTUAL_DISK_ACCESS_MASK VIRTUAL_DISK_ACCESS;
    Int64 VIRTUAL_DISK_FLAG;
    _VIRTUAL_STORAGE_TYPE VIRTUAL_STORAGE_TYPE;

    if (File.Exists(VirtualDiskPath)) {
        VIRTUAL_DISK_ACCESS = _VIRTUAL_DISK_ACCESS_MASK.VIRTUAL_DISK_ACCESS_ATTACH_ALL;
        VIRTUAL_DISK_FLAG = OPEN_VIRTUAL_DISK_FLAG_NONE;
        VIRTUAL_STORAGE_TYPE.DeviceId = VIRTUAL_STORAGE_TYPE_DEVICE_ISO;
        VIRTUAL_STORAGE_TYPE.VendorId = VENDORMICROSOFT;

        IntPtr VirtualStorPtr = IntPtr.Zero;
        VirtualStorPtr = Marshal.AllocHGlobal(Marshal.SizeOf(VIRTUAL_STORAGE_TYPE));
        Marshal.StructureToPtr(VIRTUAL_STORAGE_TYPE, VirtualStorPtr, true);

        IntPtr VirtualDiskVer = IntPtr.Zero;
        OPEN_VIRTUAL_DISK_PARAMTERS OPEN_VIRTUAL_DISK_PARAM;
        OPEN_VIRTUAL_DISK_PARAM = new OPEN_VIRTUAL_DISK_PARAMTERS {
            version = OPEN_VIRTUAL_DISK_VERSION.OPEN_VIRTUAL_DISK_VERSION_1,
            version1 = new OPEN_VIRTUAL_DISK_PARAMTERS1 { RWDepth = 0 }
        };
        VirtualDiskVer = Marshal.AllocHGlobal(Marshal.SizeOf(OPEN_VIRTUAL_DISK_PARAM));
        Marshal.StructureToPtr(OPEN_VIRTUAL_DISK_PARAM, VirtualDiskVer, true);

        RetVal = OpenVirtualDisk(ref VIRTUAL_STORAGE_TYPE, VirtualDiskPath, VIRTUAL_DISK_ACCESS, VIRTUAL_DISK_FLAG, ref OPEN_VIRTUAL_DISK_PARAM, ref pHandle);

        if ((RetVal == 0)) {
            MessageBox.Show("OpenVirtualDisk() has succeded in opening the file: \r\n" + VirtualDiskPath + "\r\nWith the file Handle: " + pHandle.ToString());
        } else {
            MessageBox.Show("OpenVirtualDisk() failed to open the file: " + VirtualDiskPath + ",\r\nWith Error Code: " + Marshal.GetLastWin32Error().ToString() + "\r\nReturn Value: " + RetVal.ToString());
        }
        Marshal.FreeHGlobal(VirtualStorPtr);
    }
}

最终解决方法 #

折腾了半天，发现问题出在两个地方：

1. 权限掩码不对：我一开始用了VIRTUAL_DISK_ACCESS_ATTACH_ALL，但ISO是只读镜像，根本不需要这么高的权限，改成VIRTUAL_DISK_ACCESS_READ（对应FILE_ACCESS_MASK_RO）就解决了参数无效的问题。

2. DllImport的字符集和参数标记错了：

   • Windows API的路径默认是Unicode的，我之前设了CharSet.Ansi，导致路径解析错误，改成CharSet.Unicode就解决了“文件未找到”的问题。
   • 给几个参数加上[In]特性，明确传递方向，避免封送的时候出问题。
   • 顺便把dll名改成小写的virtdisk.dll（其实大小写不影响，但统一规范点）。

修改后的DllImport如下：

[DllImport("virtdisk.dll", CharSet = CharSet.UNICODE, ThrowOnUnmappableChar = true, SetLastError = true)]
public extern static Int64 OpenVirtualDisk(
[In] ref _VIRTUAL_STORAGE_TYPE PVIRTUAL_STORAGE_TYPE,
string Path,
[In] _VIRTUAL_DISK_ACCESS_MASK LVIRTUAL_DISK_ACCESS_MASK,
[In] long OPEN_VIRTUAL_DISK_FLAG,
[In, Optional] ref OPEN_VIRTUAL_DISK_PARAMTERS POPEN_VIRTUAL_DISK_PARAMTERS,
[In] ref IntPtr pHandle);

改完之后再调用就成功挂载ISO了，希望同样转C#的Pascal老鸟或者WinPE开发的朋友能少踩这个坑～

内容的提问来源于stack exchange，提问作者R.McInnes-Piper