C# Signature:

[DllImport("kernel32.dll")]
static extern uint QueryDosDevice(string lpDeviceName, IntPtr lpTargetPath,
   uint ucchMax);

Alternate signature:

[DllImport("kernel32.dll")]
static extern uint QueryDosDevice(string lpDeviceName, StringBuilder lpTargetPath, int ucchMax);

User-Defined Types:

None.

Notes:

Use the second signature if you want only the current mapping for the DOS device. The first null-terminated string returned by the function contains the current mapping, and will be automatically read into the StringBuilder.

Tips & Tricks:

If you are trying to get a string array of all the Devices on your system, this is the code that I used for this.

Not sure if it's the cleanest... but it works https://www.pinvoke.net/emoticons/regular_smile.gif

Sample Code:

private static string[] QueryDosDevice()
{
    // Allocate some memory to get a list of all system devices.
    // Start with a small size and dynamically give more space until we have enough room.
    int returnSize = 0;
    int maxSize = 100;
    string allDevices = null;
    IntPtr mem;
    string [] retval = null;

    while(returnSize == 0)
    {
        mem = Marshal.AllocHGlobal(maxSize);
        if(mem != IntPtr.Zero)
        {
            // mem points to memory that needs freeing
            try
            {
                returnSize = QueryDosDevice(null, mem, maxSize);
                if(returnSize != 0)
                {
                    allDevices = Marshal.PtrToStringAnsi(mem, returnSize);
                    retval = allDevices.Split('\0');
                    break;    // not really needed, but makes it more clear...
                }
                else if(GetLastError() == ERROR_INSUFFICIENT_BUFFER)
                //maybe better
                //else if( Marshal.GetLastWin32Error() == ERROR_INSUFFICIENT_BUFFER)
                //ERROR_INSUFFICIENT_BUFFER = 122;
                {
                    maxSize *= 10;
                }
                else
                {
                    Marshal.ThrowExceptionForHR(GetLastError());
                }
            }
            finally
            {
                Marshal.FreeHGlobal(mem);
            }
        }
        else
        {
            throw new OutOfMemoryException();
        }
    }
    return retval;
}

Sample Code for second signature:

private static string GetRealPath(string path)
{
    string realPath;
    StringBuilder pathInformation = new StringBuilder(250);

    // Get the drive letter of the
     string driveLetter = Path.GetPathRoot(path).Replace("\\", "");
     QueryDosDevice(driveLetter, pathInformation, 250);

    // If drive is substed, the result will be in the format of "\??\C:\RealPath\".
    if (pathInformation.ToString().Contains("\\??\\"))
    {
       // Strip the \??\ prefix.
       string realRoot = pathInformation.ToString().Remove(0, 4);

       //Combine the paths.
       realPath = Path.Combine(realRoot, path.Replace(Path.GetPathRoot(path), ""));
    }
    else
    {
       realPath = path;
    }
    return realPath;
}

Alternative Managed API:

Do you know one? Please contribute it!

Please edit this page!

Do you have...

• helpful tips or sample code to share for using this API in managed code?
• corrections to the existing content?
• variations of the signature you want to share?
• additional languages you want to include?

Select "Edit This Page" on the right hand toolbar and edit it! Or add new pages containing supporting types needed for this API (structures, delegates, and more).