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 
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)
{
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!
