pinvoke.net: Edit: wtsapi32.wtsenumeratesessions

@msdn=http://search.microsoft.com/search/results.aspx?qu=$$$
@pinvoke=http://pinvoke.net/$$$.htm

Summary: This Terminal Services API call lists all local and remote sessions for a given server, including their state (e.g. connected, disconnected) and type (local, RDP). It is the basis for the output of qwinsta.exe.

!!!!C# Signature:
 [DllImport("wtsapi32.dll", SetLastError=true)]
 static extern int WTSEnumerateSessions(
				System.IntPtr hServer,
				int Reserved,
				int Version,
				ref System.IntPtr ppSessionInfo,
				ref int pCount);

[DllImport("wtsapi32.dll", SetLastError=true)]
 static extern void WTSEnumerateSessions(
				System.IntPtr hServer,
				ref System.IntPtr ppSessionInfo,
				ref int pCount)
 {
 	WTSEnumerateSessions(hServer,0,1,ppSessionInfo,pCount);
 }

!!!!Powershell Signature:
 $wtsenumsig = @'
 [DllImport("wtsapi32.dll", SetLastError=true)]
 public static extern int WTSEnumerateSessions(
                System.IntPtr hServer,
                int Reserved,
                int Version,
                ref System.IntPtr ppSessionInfo,
                ref int pCount);
 '@
!!!!C# Example

// Note the VB example will give you the first entry of the array n times where n is the size of the array
 using System;
 using System.Collections.Generic;
 using System.Text;
 using System.Runtime.InteropServices;

namespace TerminalServices
 {
    class TSManager
    {
        [DllImport("wtsapi32.dll", SetLastError=true)]
        static extern IntPtr WTSOpenServer([MarshalAs(UnmanagedType.LPStr)] String pServerName);

[DllImport("wtsapi32.dll")]
        static extern void WTSCloseServer(IntPtr hServer);

[DllImport("wtsapi32.dll", SetLastError=true)]
        static extern Int32 WTSEnumerateSessions(
            IntPtr hServer, 
            [MarshalAs(UnmanagedType.U4)] Int32 Reserved,
            [MarshalAs(UnmanagedType.U4)] Int32 Version, 
            ref IntPtr ppSessionInfo,
            [MarshalAs(UnmanagedType.U4)] ref Int32 pCount);

[DllImport("wtsapi32.dll")]
        static extern void WTSFreeMemory(IntPtr pMemory);

[StructLayout(LayoutKind.Sequential)]
        private struct WTS_SESSION_INFO
        {
            public Int32 SessionID;
            
            [MarshalAs(UnmanagedType.LPStr)]
            public String pWinStationName;

public WTS_CONNECTSTATE_CLASS State;
        }

public enum WTS_CONNECTSTATE_CLASS
        {
            WTSActive,
            WTSConnected,
            WTSConnectQuery,
            WTSShadow,
            WTSDisconnected,
            WTSIdle,
            WTSListen,
            WTSReset,
            WTSDown,
            WTSInit
        }

public static IntPtr OpenServer(String Name)
        {
            IntPtr server = WTSOpenServer(Name);
            return server;
        }
        public static void CloseServer(IntPtr ServerHandle)
        {
            WTSCloseServer(ServerHandle);
        }
        public static List<String> ListSessions(String ServerName)
        {
            IntPtr server = IntPtr.Zero;
            List<String> ret = new List<string>();
            server = OpenServer(ServerName);
 
            try
            {
                IntPtr ppSessionInfo = IntPtr.Zero;

Int32 count = 0;
                Int32 retval = WTSEnumerateSessions(server, 0, 1, ref ppSessionInfo, ref count);
                Int32 dataSize = Marshal.SizeOf(typeof(WTS_SESSION_INFO));

Int64 current = (int)ppSessionInfo;

if (retval != 0)
                {
                    for (int i = 0; i < count; i++)
                    {
                        WTS_SESSION_INFO si = (WTS_SESSION_INFO)Marshal.PtrToStructure((System.IntPtr)current, typeof(WTS_SESSION_INFO));
                        current += dataSize;
                        
                        ret.Add(si.SessionID + " " + si.State + " " + si.pWinStationName);
                    }
                 
                    WTSFreeMemory(ppSessionInfo);
                }
            }
            finally
            {
                CloseServer(server);
            }

return ret;
        }
    }
 }

!!!!Powershell Example
 $server = "vmtermsrv"
 $messageTitle = "FooBar"
 $message = "This is a test...  This is only a test"
 $timeout = 60;
 
 $wtssig = @'
 namespace mystruct {
 using System;
 using System.Runtime.InteropServices;
     [StructLayout(LayoutKind.Sequential)]
     public struct WTS_SESSION_INFO
     {
         public Int32 SessionID;
 
         [MarshalAs(UnmanagedType.LPStr)]
         public String pWinStationName;
 
         public WTS_CONNECTSTATE_CLASS State;
     }
 
     public enum WTS_CONNECTSTATE_CLASS
     {
         WTSActive,
         WTSConnected,
         WTSConnectQuery,
         WTSShadow,
         WTSDisconnected,
         WTSIdle,
         WTSListen,
         WTSReset,
         WTSDown,
         WTSInit
     } 
     }
 '@
 
 
 add-type  $wtssig
 
 $wtsenumsig = @'
 [DllImport("wtsapi32.dll", SetLastError=true)]
 public static extern int WTSEnumerateSessions(
                 System.IntPtr hServer,
                 int Reserved,
                 int Version,
                 ref System.IntPtr ppSessionInfo,
                 ref int pCount);
 '@
 
 $wtsopensig = @'
 [DllImport("wtsapi32.dll", SetLastError=true)]
 public static extern IntPtr WTSOpenServer(string pServerName);
 '@
 
 $wtsSendMessagesig = @'
 [DllImport("wtsapi32.dll", SetLastError = true)]
     public static extern bool WTSSendMessage(
         IntPtr hServer,
         [MarshalAs(UnmanagedType.I4)] int SessionId,
         String pTitle,
         [MarshalAs(UnmanagedType.U4)] int TitleLength,
         String pMessage,
         [MarshalAs(UnmanagedType.U4)] int MessageLength,
         [MarshalAs(UnmanagedType.U4)] int Style,
         [MarshalAs(UnmanagedType.U4)] int Timeout,
         [MarshalAs(UnmanagedType.U4)] out int pResponse,
         bool bWait);
 '@
 
 $wtsenum = add-type -MemberDefinition $wtsenumsig -Name PSWTSEnumerateSessions -Namespace GetLoggedOnUsers -PassThru
 $wtsOpen = add-type -MemberDefinition $wtsopensig -name PSWTSOpenServer -Namespace GetLoggedOnUsers -PassThru
 $wtsmessage = Add-Type -MemberDefinition $wtsSendMessagesig -name PSWTSSendMessage -Namespace GetLoggedOnUsers -PassThru
 
 
 
 [long]$count = 0
 [long]$ppSessionInfo = 0
 
 $server = $wtsOpen::WTSOpenServer($server)
 [long]$retval = $wtsenum::WTSEnumerateSessions($server,0,1,[ref]$ppSessionInfo,[ref]$count)
 $datasize = [system.runtime.interopservices.marshal]::SizeOf([System.Type][mystruct.WTS_SESSION_INFO])
 $Responses = @()
 if ($retval -ne 0){
     for ($i = 0; $i -lt $count; $i++){
         $element =  [system.runtime.interopservices.marshal]::PtrToStructure($ppSessionInfo + ($datasize * $i),[System.type][mystruct.WTS_SESSION_INFO])
         $element
         $resp = ""
         $wtsmessage::WTSSendMessage($server, $element.SessionID,$messageTitle,$messageTitle.Length,$message,$message.Length,0,$timeout,[ref]$resp,$true)
         $responses += $resp;
     }
 
 }
 $responses

!!!!VB Signature:

<DllImport("wtsapi32.dll", _
        bestfitmapping:=True, _
        CallingConvention:=CallingConvention.StdCall, _
        CharSet:=CharSet.Auto, _
        EntryPoint:="WTSEnumerateSessions", _
        setlasterror:=True, _
        ThrowOnUnmappableChar:=True)> _
    Private Shared Function WTSEnumerateSessions( _
        ByVal hServer As IntPtr, _
        <MarshalAs(UnmanagedType.U4)> _
        ByVal Reserved As Int32, _
        <MarshalAs(UnmanagedType.U4)> _
        ByVal Version As Int32, _
        ByRef ppSessionInfo As IntPtr, _
        <MarshalAs(UnmanagedType.U4)> _
        ByRef pCount As Int32) As Int32
    End Function

!!!!User-Defined Types:

Private Enum WTS_CONNECTSTATE_CLASS
        WTSActive
        WTSConnected
        WTSConnectQuery
        WTSShadow
        WTSDisconnected
        WTSIdle
        WTSListen
        WTSReset
        WTSDown
        WTSInit
    End Enum

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)> _
    Private Structure WTS_SESSION_INFO
        Dim SessionID As Int32 'DWORD integer
        Dim pWinStationName As String ' integer LPTSTR - Pointer to a null-terminated string containing the name of the WinStation for this session
        Dim State As WTS_CONNECTSTATE_CLASS
    End Structure

!!!!Notes:
None.

!!!!Tips & Tricks:
Please add some!

!!!!Sample Code:
 Option Explicit On 
 Option Strict On

Imports System.Runtime.InteropServices

Public Class ManagedWTSAPI

Friend Structure strSessionsInfo
        Dim SessionID As Integer
        Dim StationName As String
        Dim ConnectionState As String
    End Structure

<DllImport("wtsapi32.dll", _
        bestfitmapping:=True, _
        CallingConvention:=CallingConvention.StdCall, _
        CharSet:=CharSet.Auto, _
        EntryPoint:="WTSEnumerateSessions", _
        setlasterror:=True, _
        ThrowOnUnmappableChar:=True)> _
    Private Shared Function WTSEnumerateSessions( _
        ByVal hServer As IntPtr, _
        <MarshalAs(UnmanagedType.U4)> _
        ByVal Reserved As Int32, _
        <MarshalAs(UnmanagedType.U4)> _
        ByVal Vesrion As Int32, _
        ByRef ppSessionInfo As IntPtr, _
        <MarshalAs(UnmanagedType.U4)> _
        ByRef pCount As Int32) As Int32
    End Function

<DllImport("wtsapi32.dll")> _
    Private Shared Sub WTSFreeMemory(ByVal pMemory As IntPtr)
    End Sub

<DllImport("wtsapi32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
     Private Shared Function WTSOpenServer(ByVal pServerName As String) As IntPtr
    End Function

<DllImport("wtsapi32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
     Private Shared Sub WTSCloseServer(ByVal hServer As IntPtr)
    End Sub

Friend Function GetSessions(ByVal ServerName As String) As strSessionsInfo()
        Dim ptrOpenedServer As IntPtr
        Dim RetVal As strSessionsInfo()
        Try
            ptrOpenedServer = WTSOpenServer(ServerName)
            Dim FRetVal As Int32
            Dim ppSessionInfo As IntPtr = IntPtr.Zero
            Dim Count As Int32 = 0
            Try
                FRetVal = WTSEnumerateSessions(ptrOpenedServer, 0, 1, ppSessionInfo, Count)
                If FRetVal <> 0 Then
                    Dim sessionInfo() As WTS_SESSION_INFO = New WTS_SESSION_INFO(Count) {}
                    Dim i As Integer
                    Dim DataSize = Marshal.SizeOf(New WTS_SESSION_INFO)
                    Dim current As Int64
                    current = ppSessionInfo.ToInt64
                    For i = 0 To Count - 1 ' Step i + 1
                        sessionInfo(i) = CType(Marshal.PtrToStructure(New IntPtr(current), GetType(WTS_SESSION_INFO)), WTS_SESSION_INFO)
                        current = current + DataSize
                    Next
                    WTSFreeMemory(ppSessionInfo)
                    Dim tmpArr(sessionInfo.GetUpperBound(0)) As strSessionsInfo
                    For i = 0 To tmpArr.GetUpperBound(0)
                        tmpArr(i).SessionID = sessionInfo(i).SessionID
                        tmpArr(i).StationName = sessionInfo(i).pWinStationName
                        tmpArr(i).ConnectionState = GetConnectionState(sessionInfo(i).State)
                    Next
                    ReDim sessionInfo(-1)
                    RetVal = tmpArr
                Else
                    Throw New ApplicationException("No data retruned")
                End If
            Catch ex As Exception
                Throw New Exception(ex.Message & vbCrLf & System.Runtime.InteropServices.Marshal.GetLastWin32Error)
            End Try
        Catch ex As Exception
            Throw New Exception(ex.Message)
            Exit Function
        Finally
            WTSCloseServer(ptrOpenedServer)
        End Try

Return RetVal
    End Function

Private Function GetConnectionState(ByVal State As WTS_CONNECTSTATE_CLASS) As String
        Dim RetVal As String
        Select Case State
            Case WTS_CONNECTSTATE_CLASS.WTSActive
                RetVal = "Active"
            Case WTS_CONNECTSTATE_CLASS.WTSConnected
                RetVal = "Connected"
            Case WTS_CONNECTSTATE_CLASS.WTSConnectQuery
                RetVal = "Query"
            Case WTS_CONNECTSTATE_CLASS.WTSDisconnected
                RetVal = "Disconnected"
            Case WTS_CONNECTSTATE_CLASS.WTSDown
                RetVal = "Down"
            Case WTS_CONNECTSTATE_CLASS.WTSIdle
                RetVal = "Idle"
            Case WTS_CONNECTSTATE_CLASS.WTSInit
                RetVal = "Initializing."
            Case WTS_CONNECTSTATE_CLASS.WTSListen
                RetVal = "Listen"
            Case WTS_CONNECTSTATE_CLASS.WTSReset
                RetVal = "reset"
            Case WTS_CONNECTSTATE_CLASS.WTSShadow
                RetVal = "Shadowing"
            Case Else
                RetVal = "Unknown connect state"
        End Select
        Return RetVal
    End Function

End Class
!!!!Alternative Managed API:
Cassia on google code: https://code.google.com/p/cassia/

Documentation: WTSEnumerateSessions@msdn on MSDN