How Do I Get the Assigned Drive Letter When Mounting an ISO with WMI in C#?

Question

This is the code that I am using to mount the ISO

// With help of WMICodeCreator
ManagementObject mo = new ManagementObject("root\\Microsoft\\Windows\\Storage",
    "MSFT_DiskImage.ImagePath='" + isoFile + "',StorageType=1",
    null);

// Obtain in-parameters for the method
ManagementBaseObject inParams = mo.GetMethodParameters("Mount");

// Execute the method and obtain the return values.
ManagementBaseObject outParams = mo.InvokeMethod("Mount", inParams, null);

The outParams just returns a bool as documented here.

If I issue this command:

mo.Get();
string device = mo.GetPropertyValue("DevicePath");

... the device string shows \\.\CDROM0. It shows this value even if I mount a second ISO.

Answer 1

I found a solution in a C++ project created by Jim Dale MountISO.wmi on GitHub

Here is my final C# class for automated mounting and unmounting iso images in Windows 8+ and retrieving the auto-mounted drive letter. It is dramatically faster and more reliable than the typical PowerShell method.

using System.Management;
using System.Threading;

namespace IsoTools
{
    public static class IsoMounter
    {
        private const string WmiScope = @"root\Microsoft\Windows\Storage";

        /// <summary>Mounts an ISO disc image file.</summary>
        /// <param name="isoPath">
        /// The full path of the ISO to be mounted.
        /// </param>
        /// <returns>
        /// A System.Char representing a drive volume letter.
        /// </returns>
        public static char Mount(string isoPath)
        {
            string isoObjectPath = BuildIsoObjectPath(isoPath);
            using (var isoObject =
                new ManagementObject(WmiScope, isoObjectPath, null))
            {
                using (ManagementBaseObject inParams =
                    isoObject.GetMethodParameters("Mount"))
                {
                    isoObject.InvokeMethod("Mount", inParams, null);
                }
            }

            // The query used to retrieve the volume letter for an image.
            string volumeQuery = "ASSOCIATORS OF {" + isoObjectPath + "}" +
                "WHERE AssocClass = MSFT_DiskImageToVolume " +
                "ResultClass = MSFT_Volume";

            char mountLetter = '\0';
            using (var query =
                new ManagementObjectSearcher(WmiScope, volumeQuery))
            {
                // Run query until drive is mounted
                while (mountLetter < 65)
                {
                    Thread.Sleep(50);
                    using (ManagementObjectCollection queryCollection =
                        query.Get())
                    {
                        foreach (ManagementBaseObject item in queryCollection)
                        {
                            mountLetter = item["DriveLetter"].ToString()[0];
                        }
                    }
                }
            }

            return mountLetter;
        }

        /// <summary>Dismount an ISO disc image file.</summary>
        /// <param name="isoPath">
        /// The full path of the ISO to be mounted.
        /// </param>
        public static void Dismount(string isoPath)
        {
            using (var isoObject = new ManagementObject(
                WmiScope,
                BuildIsoObjectPath(isoPath),
                null))
            {
                using (ManagementBaseObject inParams =
                    isoObject.GetMethodParameters("Dismount"))
                {
                    isoObject.InvokeMethod("Dismount", inParams, null);
                }
            }
        }

        /// <summary>Creates the WMI pathstring for an ISO image.</summary>
        /// <param name="isoPath">
        /// The full path of the ISO to be mounted.
        /// </param>
        /// <returns>A System.String representing a WMI pathstring.</returns>
        private static string BuildIsoObjectPath(string isoPath)
        {
            // Single quoted paths do not allow escaping of single quotes
            // within the ImagePath.  Use double quotes and escape backslashes.
            return "MSFT_DiskImage.ImagePath=\"" +
                isoPath.Replace("\\", "\\\\") +
                "\",StorageType=1";
        }
    }
}