WTSEnumerateSessions

**Nicholas Paldino [.NET/C# MVP]** · Nov 16 '05, 12:10 PM

Re: WTSEnumerateSes sions

Mészáros,

The reason for this is because the runtime doesn't know how many
elements to marshal back from the unmanaged realm.

Also, a few of your definitions are off. Here are the definitions you
should have:

enum WTS_CONNECTSTAT E_CLASS
{
WTSActive,
WTSConnected,
WTSConnectQuery , // This was misspelled.
WTSShadow,
WTSDisconnected ,
WTSIdle,
WTSListen,
WTSReset,
WTSDown,
WTSInit
};

[StructLayout(La youtKind.Sequen tial, CharSet=CharSet .Auto)]
struct WTS_SESSION_INF O
{
public int SessionId;
public string pWinStationName ;
public WTS_CONNECTSTAT E_CLASS State;
}

You need to define the function differently as well as make some
corrections.

[DllImport("wtsa pi32.dll", CharSet=CharSet .Auto)]
private static extern bool WTSEnumerateSes sions(
// Always use IntPtr for handles, and then something derived from
SafeHandle in .NET 2.0
IntPtr hServer,
// Not required, but a good practice.
[MarshalAs(Unman agedType.U4)]
int Reserved,
[MarshalAs(Unman agedType.U4)]
int Version,
// You are going to create the memory block yourself.
ref IntPtr ppSessionInfo,
[MarshalAs(Unman agedType.U4)]
ref int pCount);

You also need the following definition:

[DllImport("wtsa pi32.dll")]
private static extern void WTSFreeMemory(I ntPtr pMemory);

Now, to make the call, you do this:

// Create the pointer that will get the buffer.
IntPtr buffer = IntPtr.Zero;

// The count.
int count = 0;

// Make the call.
if (WTSEnumerateSe ssions(IntPtr.Z ero, 0, 1, ref buffer, ref count))
{
// Marshal to a structure array here. Create the array first.
WTS_SESSION_INF O[] sessionInfo = new WTS_SESSION_INF O[count];

// Cycle through and copy the array over.
for (int index = 0; index < count; index++)
// Marshal the value over.
sessionInfo[index] = Marshal.PtrToSt ructure(buffer +
(sizeof(WTS_SES SION_INFO) * index), typeof(WTS_SESS ION_INFO));

// Work with the array here.
}

// Close the buffer.
WTSFreeMemory(b uffer);

Hope this helps.

--
- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard. caspershouse.co m

"Mészáros Tamás" <mesztam@sch.bm e.hu> wrote in message
news:uC6hXeKoEH A.536@TK2MSFTNG P11.phx.gbl...[color=blue]
> Hi!
>
> I want to get information about the state of TS-Sessions, and I've tried
> it the following way:
>
> ------------------------------------------------------
> enum WTS_CONNECTSTAT E_CLASS
> {
> WTSActive,
> WTSConnected,
> TSConnectQuery,
> WTSShadow,
> WTSDisconnected ,
> WTSIdle,
> WTSListen,
> WTSReset,
> WTSDown,
> WTSInit
> };
>
> struct WTS_SESSION_INF O
> {
> public int SessionId;
> public string pWinStationName ;
> public WTS_CONNECTSTAT E_CLASS State;
> }
>
> [DllImport("wtsa pi32")]
> private static extern bool WTSEnumerateSes sions(int hServer, int reserved,
> int version, ref WTS_SESSION_INF O[] ppSessionInfo, ref int Count);
>
> ...
>
> WTS_SESSION_INF O[] ppSessionInfo = new WTS_SESSION_INF O[20]; /*I must
> initialize it, because I can't pass it to a function uninitialized*/
> int Count = 0;
> WTS_SESSION_INF O wts;
>
> WTSEnumerateSes sions(0, 0, 1, ref ppSessionInfo, ref Count );
>
> ...
> -----------------------------------------------------------------------
> After the WTSEnumerateSes sions function returns, I can find the correct
> number in the Count variable, but the ppSessionInfo allways has only one
> element and it doesn't contain any information about the other sessions.
>
> Could someone correct this code-part or send me a working example?
>
> Thanks in advance,
>
> Tamas Meszaros[/color]

**Mészáros Tamás** · Nov 16 '05, 12:10 PM

Re: WTSEnumerateSes sions

with small modifications it has worked fine, thanks a lot.

Tamas Meszaros

Nicholas Paldino [.NET/C# MVP] wrote:[color=blue]
> Mészáros,
>
> The reason for this is because the runtime doesn't know how many
> elements to marshal back from the unmanaged realm.
>
> Also, a few of your definitions are off. Here are the definitions you
> should have:
>
> enum WTS_CONNECTSTAT E_CLASS
> {
> WTSActive,
> WTSConnected,
> WTSConnectQuery , // This was misspelled.
> WTSShadow,
> WTSDisconnected ,
> WTSIdle,
> WTSListen,
> WTSReset,
> WTSDown,
> WTSInit
> };
>
> [StructLayout(La youtKind.Sequen tial, CharSet=CharSet .Auto)]
> struct WTS_SESSION_INF O
> {
> public int SessionId;
> public string pWinStationName ;
> public WTS_CONNECTSTAT E_CLASS State;
> }
>
> You need to define the function differently as well as make some
> corrections.
>
> [DllImport("wtsa pi32.dll", CharSet=CharSet .Auto)]
> private static extern bool WTSEnumerateSes sions(
> // Always use IntPtr for handles, and then something derived from
> SafeHandle in .NET 2.0
> IntPtr hServer,
> // Not required, but a good practice.
> [MarshalAs(Unman agedType.U4)]
> int Reserved,
> [MarshalAs(Unman agedType.U4)]
> int Version,
> // You are going to create the memory block yourself.
> ref IntPtr ppSessionInfo,
> [MarshalAs(Unman agedType.U4)]
> ref int pCount);
>
> You also need the following definition:
>
> [DllImport("wtsa pi32.dll")]
> private static extern void WTSFreeMemory(I ntPtr pMemory);
>
> Now, to make the call, you do this:
>
> // Create the pointer that will get the buffer.
> IntPtr buffer = IntPtr.Zero;
>
> // The count.
> int count = 0;
>
> // Make the call.
> if (WTSEnumerateSe ssions(IntPtr.Z ero, 0, 1, ref buffer, ref count))
> {
> // Marshal to a structure array here. Create the array first.
> WTS_SESSION_INF O[] sessionInfo = new WTS_SESSION_INF O[count];
>
> // Cycle through and copy the array over.
> for (int index = 0; index < count; index++)
> // Marshal the value over.
> sessionInfo[index] = Marshal.PtrToSt ructure(buffer +
> (sizeof(WTS_SES SION_INFO) * index), typeof(WTS_SESS ION_INFO));
>
> // Work with the array here.
> }
>
> // Close the buffer.
> WTSFreeMemory(b uffer);
>
> Hope this helps.
>
>[/color]

WTSEnumerateSessions

WTSEnumerateSessions

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