GetUserObjectInformation

Sorry.  Maybe I did not explain it correctly.  What I need is to get the desktop name.  For instance 16 represents the length needed for the name.  So in actual there has to be something that I need to do in order to change 16 to a string like "Default" which should be the correct name for my current desktop.  I have tried using lpNeeded() As Byte and change the API declaration but that gives me a protected memory error.  I was thinking about using IntPtr and then trying to get the string value of that but I do not know where to begin with taking a memory location and turning it back into  a string.  Unless that is not what I need to do.

Jason

Hey, why aren't you using the Environment class? It's a default class in the framework containing all kinds of information about the client the application is running on. i.e: MsgBox(Environment.MachineName).

I am trying to get the desktop name.  Not a special folder.  My program creates new desktops and in order for me to be able to use it across each desktop it needs to get the name of the current desktop so it can check the appropriate one in the menu.  It is a long story but I will try to explain it best.

First thing happens is that the user starts the program and I need to get the desktop name so I know which desktop I am currently on.  This is largely due to the fact that I can not open a process in another desktop that already has a window in a different one.  So I need to use the CreateProcess API so I can just create another instance of it in a different desktop which will allow me to switch desktops.  That is where the GetUserObjectInformation comes in.  Because you can get the windows station name or desktop name.  Since the desktops are created by the user this is the easiest and best method.  Here is a link to MS GetUserObjectInformation which may help you help me.  Thanks.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/getuserobjectinformation.asp

Jason

Increased Points.  Maybe a little more difficult than I originally thought.

Bob,

I did try that once but no where close to how you have it.  Tried it your way and it goes through the code fine but when I try to msg builder.length I get 0.  Now from my understanding the nLength needs to be the same as lpNeeded in order for it to return the name.  But if that is not the case then how do I get the name from the method that you have provided.  Thanks again for the help.  And if you don't know then that is fine I will still award you the points.  Thanks.

Jason

Jason,
I'll see if I can try it tomorrow.  I didn't have time to test today.

Bob

Okay.  Thanks.

Jason

Jason,
This is what I have so far, but it still doesn't work.  I get some pretty strange errors--this is not a trivial pursuit.

  Private Const UOI_FLAGS = 1
  Private Const UOI_NAME = 2
  Private Const UOI_TYPE = 3
  Private Const UOI_USER_SID = 4

  <DllImport("user32.dll", SetLastError:=True)> _
  Private Shared Function GetThreadDesktop(<MarshalAs(UnmanagedType.I4)> ByVal dwThreadId As Integer) As IntPtr
  End Function

  <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
  Private Shared Function GetUserObjectInformation(ByVal hObj As IntPtr, ByVal nIndex As Int32, ByRef pvInfo As Byte(), <MarshalAs(UnmanagedType.I4)> ByVal nLength As Integer, <MarshalAs(UnmanagedType.I4)> ByRef lpnLengthNeeded As Integer) As Boolean
  End Function

  <DllImport("kernel32.dll")> _
  Private Shared Function GetCurrentThreadId() As Integer
  End Function


  Private Function GetDesktopName() As String

    Const ERROR_INSUFFICIENT_BUFFER& = 122
    Const ERROR_PROC_NOT_FOUND& = 127

    Dim buffer(15) As Byte
    Dim lpNeeded As Integer
    Dim threadID As Integer = GetCurrentThreadId()
    Dim desktop As IntPtr = GetThreadDesktop(threadID)

    GetUserObjectInformation(desktop, UOI_NAME, buffer, 16, lpNeeded)

    If Err.LastDllError = ERROR_INSUFFICIENT_BUFFER Then
      Throw New ArgumentException("Insufficient buffer specified")
    End If

    If lpNeeded <> 0 Then
      ReDim buffer(lpNeeded - 1)
      GetUserObjectInformation(desktop, UOI_NAME, buffer, lpNeeded, lpNeeded)

      If Err.LastDllError = ERROR_PROC_NOT_FOUND Then
        Throw New ArgumentException("Procedure not found.")
      End If

    End If

  End Function  'GetDesktopName

Bob

Bob,

Well, unfortunately as you stated it did not work.  I don't know exactly what is wrong but I went ahead and posted on the MS Forums about this.  Hopefully someone will be able to help me out here.  I have tried just about every combination that I can think of and still nothing.  If you or anyone else has a suggestion please let me know.  I am out of thoughts here.  If I don't get an answer then I will still award you the points because I know that you have to be close.  Maybe just a little more tweaking and I will get it.  I will keep trying and post regular updates with my progress and check back often for any more tips.  Thanks.

jason

I was hoping that it might work for you :(

Bob

Well let me to this.  Here is the C example of what I am trying to do.  Maybe this will help us.

CString CMFDeskTopHelper::GetCurrentDesktop()
{
      try
      {
            HDESK hDesk = GetThreadDesktop(GetCurrentThreadId());
            if(hDesk == 0)
            {
                  m_szLastError = "Unable to GetThreadDesktop";
                  return "";
            }

            DWORD dwNeed;
            GetUserObjectInformation(hDesk, UOI_NAME, NULL, 0, &dwNeed);
            if(dwNeed!=0)
            {
                  char *szDeskName = (char*)malloc(dwNeed);
                  if(szDeskName==NULL)
                  {
                        m_szLastError = "Unable to allocate memory";
                        return "";
                  }
                  if(FALSE == GetUserObjectInformation(hDesk, UOI_NAME, (void*)szDeskName, dwNeed, &dwNeed))
                  {
                        m_szLastError = "Unable to GetUserObjectInformation(successive)";
                        return "";
                  }

                  CString szDName(szDeskName);
                  free(szDeskName);
                  return szDName;
            }
            else
            {
                  m_szLastError = "Unable to GetUserObjectInformation(initial)";
                  return "";
            }

            return "";
      }
      catch(...)
      {
            m_szLastError = "Exception caught in GetCurrentDesktop()";
            return "";
      }
}

I know, I have seen that, but it doesn't help much :(

Bob

I know it didn't really help me either.  I followed it to a tee and still nothing.  Oh well.  I will keep trying and thanks for the help.

Jason

Bob,

You were so close it was not funny.  Here is what I got from the MS Forums

API Declaration
Public Declare Function GetUserObjectInformation Lib "user32" Alias "GetUserObjectInformationA" (ByVal hObj As IntPtr, ByVal nIndex As Int32, ByVal pvInfo As System.Text.StringBuilder, ByVal nLength As Byte, ByRef lpnLengthNeeded As Integer) As Boolean


Form1_Load Event

        Dim lengthNeeded As Integer
        Dim pvInfo As New System.Text.StringBuilder

        GetUserObjectInformation(GetThreadDesktop(GetCurrentThreadId()), UOI_NAME, pvInfo, Nothing, lengthNeeded)

        If lengthNeeded <> 0 Then
            GetUserObjectInformation(GetThreadDesktop(GetCurrentThreadId()), UOI_NAME, pvInfo, lengthNeeded, lengthNeeded)
            MsgBox(pvInfo.ToString)
        End If


And wouldn't you know it.  It Returns Default.  Voila.

Thanks man, you still get the points for being that dang close.

Jason