WNetGetUniversalName Error 1201

DanRoche · January 24th, 2008, 11:38 AM

Hi all,

This is an API question

I'm trying to get the UNC Path from a mapped drive. I call it once and get the ERROR_MORE_DATA code, so I call it a second time and I get the ERROR_CONNECTION_UNAVAIL code, which says "The device is not currently connected but it is a remembered connection." I'm kind of lost on that because I can see that the device is connected.

Code:

[DllImport("mpr.dll")]
private static extern int WNetGetUniversalName (string lpLocalPath,
int dwInfoLevel, ref UNIVERSAL_NAME_INFO lpBuffer, ref int lpBufferSize);

[DllImport("mpr", CharSet=CharSet.Auto)]
protected static extern int WNetGetUniversalName (string lpLocalPath,
int dwInfoLevel, IntPtr lpBuffer, ref int lpBufferSize);

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
private struct UNIVERSAL_NAME_INFO
{
[MarshalAs(UnmanagedType.LPTStr)]
public string lpUniversalName;
}

//
//Constants
//
protected const int NO_ERROR = 0;
protected const int ERROR_MORE_DATA = 234;
protected const int ERROR_NOT_CONNECTED = 2250;
protected const int UNIVERSAL_NAME_INFO_LEVEL = 1;        
protected const int ERROR_CONNECTION_UNAVAIL = 1201;

UNIVERSAL_NAME_INFO rni = new UNIVERSAL_NAME_INFO();
int bufferSize = Marshal.SizeOf(rni);

int nRet = WNetGetUniversalName(mappedDrive, UNIVERSAL_NAME_INFO_LEVEL,ref rni, ref bufferSize);

if (ERROR_MORE_DATA == nRet)
{
    IntPtr pBuffer = Marshal.AllocHGlobal(bufferSize);;
    try
    {
        nRet = WNetGetUniversalName(mappedDrive, UNIVERSAL_NAME_INFO_LEVEL,pBuffer, ref bufferSize);
//
// RETURNS ERROR 1201 = ERROR_CONNECTION_UNAVAIL

Any ideas? I'm using Windows 2000

samjudson · January 25th, 2008, 07:14 AM

Have you seen the PInvoke page?

http://www.pinvoke.net/default.aspx/...ersalName.html

Your first call doesn't look quite the same to me.

/- Sam Judson : Wrox Technical Editor -/

DanRoche · January 25th, 2008, 10:51 AM

Quote:

quote:Originally posted by samjudson
Have you seen the PInvoke page?

http://www.pinvoke.net/default.aspx/...ersalName.html

Your first call doesn't look quite the same to me.

/- Sam Judson : Wrox Technical Editor -/

I had not seen the pinvoke page, thank you. I'm going to make some changes so it's like that.

I should also note that my code WORKS as an windows form app (I click a drive letter and it shows me the unc path). But I want it to work as a service, and that's when I get the error.

DanRoche · January 25th, 2008, 11:56 AM

Bah, I stumbled across the reason on MSDN:

http://msdn2.microsoft.com/en-us/library/aa385453.aspx

If the network connection was made using the Microsoft LAN Manager network, and the calling application is running in a different logon session than the application that made the connection, a call to the WNetGetConnection function for the associated local device will fail. The function fails with ERROR_NOT_CONNECTED or ERROR_CONNECTION_UNAVAIL. This is because a connection made using Microsoft LAN Manager is visible only to applications running in the same logon session as the application that made the connection. (To prevent the call to WNetGetConnection from failing it is not sufficient for the application to be running in the user account that created the connection.)