pinvoke.net: Edit: kernel32.QueryDosDevice

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Summary: The QueryDosDevice API

!!!!C# Signature:
 [DllImport("kernel32.dll", SetLastError = true)]
 static extern uint QueryDosDevice(string lpDeviceName, IntPtr lpTargetPath, uint ucchMax);

!!!!Alternate C# signature:
 [DllImport("kernel32.dll", SetLastError = true)]
 static extern uint QueryDosDevice(string lpDeviceName, StringBuilder lpTargetPath, int ucchMax);

!!!!VB.NET Signature:
 <DllImport("Kernel32.dll", EntryPoint:="QueryDosDevice")>
 Public Shared Function QueryDosDevice(lpDeviceName As String, lpTargetPath As System.Text.StringBuilder, ucchMax As Integer) As Integer
 End Function

!!!!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 :-)

!!!!VB.NET Sample Code:

' Use the VB.NET signature above with this code. Converting the C#
 ' signatures will not work.
 Private Function QueryDosDevice(ByVal device As String) As List(Of String)

Dim returnSize As Integer = 0
        Dim maxSize As UInteger = 65536
        Dim allDevices As String = Nothing
        Dim mem As IntPtr
        Dim retval() As String = Nothing
        Dim results As New List(Of String)

' Convert an empty string into Nothing, so 
        ' QueryDosDevice will return everything available.
        If device.Trim = "" Then device = Nothing

While returnSize = 0
            mem = Marshal.AllocHGlobal(CInt(maxSize))
            If mem <> IntPtr.Zero Then
                Try
                    returnSize = CInt(QueryDosDevice(device, mem, maxSize))
                    If returnSize <> 0 Then
                        allDevices = Marshal.PtrToStringAuto(mem, returnSize)
                        retval = allDevices.Split(ControlChars.NullChar)
                        Exit Try
                    Else
                        ' This query produced no results. Exit the loop.
                        returnSize = -1
                    End If
                Finally
                    Marshal.FreeHGlobal(mem)
                End Try
            Else
                Throw New OutOfMemoryException()
            End If
        End While

If retval IsNot Nothing Then
            For Each result As String In retval
                If result.Trim <> "" Then results.Add(result)
            Next
        End If

Return results
 End Function

!!!!C# 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 alternate C# 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!

Documentation: QueryDosDevice@msdn on MSDN