Vista - Unmanaged C++ client invoke C# component to Add PSSnapin Failed

My DotNetServer.dll component contains the following codes:
i used Regasm.exe to register this component as a COM component
C# Client Invoke this interface always pass. unmanaged c++ client invoke
function "DiagnosticCom()" successful,but failed at "Connect()",
Details as below
************************DotNetServer.dll******************************
using System;
using System.Runtime.InteropServices;
using System.Collections.ObjectModel;
using System.Management.Automation;
using System.Management.Automation.Runspaces;
using Microsoft.SystemCenter.VirtualMachineManager;
using Microsoft.SystemCenter.VirtualMachineManager.Remoting;

namespace DotNetServer
{
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("0E242803-A7E4-4ae4-B6E0-E693090598EB")]
public interface IDotComServer
{
int Connect(string serverName, Int32 tcpPort);
string DiagnosticCom(string name);
}

[ClassInterface(ClassInterfaceType.None)]
[ProgId("DotNetServer.DotComServer")]
[Guid("F0CD6959-42B4-46f4-B1C9-CC88F626417A")]
public class DotComServer : IDotComServer
{
public DotComServer() { }

public int Connect(string serverName, Int32 tcpPort)
{
RunspaceConfiguration _config = null;
_config = RunspaceConfiguration.Create();
PSSnapInException ex = null;
//Failed AT

_config.AddPSSnapIn("Microsoft.SystemCenter.VirtualMachineManager", out ex);

if (ex != null)
throw ex;

using (Runspace runspace =
RunspaceFactory.CreateRunspace(_config))
{
runspace.Open();

Pipeline pipeline = runspace.CreatePipeline();

Command cmd = new Command("Get-VMMServer");
cmd.Parameters.Add("ComputerName", serverName);
cmd.Parameters.Add("TCPPort", tcpPort);

Collection<PSObject> result = null;
pipeline.Commands.Add(cmd);
result = pipeline.Invoke();

pipeline.Stop();
runspace.Close();
if (result != null && result.Count > 0) return 0;
}
return 1;
}

public string DiagnosticCom(string name)
{
return name;
}
}
}
************************************End of
DotNetServer*******************************
************************************DotNetClient*************************************
<<The following C# codes work well>>
using System;
namespace DotNetClient
{
class Program
{
static void Main(string[] args)
{
DotNetServer.DotComServer server = new
DotNetServer.DotComServer();
string strResult = server.DiagnosticCom("Hello");
int result = server.Connect("WIN-7G3JBRL3JBW.contoso.com", 8100);
}
}
}
************************************Unmanaged C++
Client*************************
<<always failed at : spServer->Connect("WIN-7G3JBRL3JBW.contoso.com",8100)>>>


#include "stdafx.h"
#include <iostream>
#import "D:\Projects\SolutionCom\DotNetServer\bin\Debug\DotNetServer.tlb"

using namespace std;
using namespace DotNetServer;

int _tmain(int argc, _TCHAR* argv[])
{
HRESULT hr;
hr = CoInitialize(NULL);
try
{
IDotComServerPtr spServer;
hr = spServer.CreateInstance("DotNetServer.DotComServer");
cout<<spServer->DiagnosticCom("OK")<<endl; //
****************work well**********************
long result =
spServer->Connect("WIN-7G3JBRL3JBW.contoso.com",8100); //
****************always failed at
--->_config.AddPSSnapIn("Microsoft.SystemCenter.VirtualMachineManager", out
ex);<-----
}
catch(_com_error& e)
{
cout<<e.ErrorMessage()<<endl; ******************Error Message "invalid
paramter"
}

CoUninitialize();
return 0;
}
***********************************************************