Access denied when using powershell in C# code , then running it from IIS

Hi ,

I need to execute below PowerShell command from C# code. This command results Users list who has access permissions to particular user.

Get-Mailbox -resultsize unlimited | Get-MailboxPermission | Where {(!$_.isinherited) -and ($_.User -like 'ADMIN\ExchangeAdmin') -and  ($_.accessrights -contains "fullaccess")  } | Select Identity,User

I am already done it , getting users list successfully in C# code .  code working fine  in visual studio.

but same code running from IIS getting Access denied . i tried to resolve it , but not yet succeed.

please see the link for my code.

http://social.technet.microsoft.com/Forums/office/en-US/f97b1c19-6fb4-4b77-9afa-eeae0988bd64/exchange-service-api-is-not-working-after-code-published-in-iis-but-locally-it-is-working-please?forum=exchangesvrdevelopment

so , i would like to change the code.

below code working fine in IIS . how can i call above power shell command from below C# code ?

 SecureString password = new SecureString();
                 string str_password = "xxxxx";
                 string username = "Administrator@admin.com";
                 foreach (char x in str_password) { password.AppendChar(x); }
                 PSCredential credential = new PSCredential(username, password);

                 WSManConnectionInfo connectionInfo = new WSManConnectionInfo(new Uri("http://ExchangeServer.admin.com/powershell/Microsoft.Exchange"), "http://schemas.microsoft.com/powershell/Microsoft.Exchange", credential);

                 Runspace runspace = RunspaceFactory.CreateRunspace(connectionInfo);

                 PowerShell powershell = PowerShell.Create();

                 PSCommand command = new PSCommand();
                 command.AddCommand("Get-Mailbox");
                 command.AddParameter("ResultSize", int.MaxValue);
                 powershell.Commands = command;
                 runspace.Open();
                 powershell.Runspace = runspace;
                 Collection<PSObject> usersList = powershell.Invoke();
                 runspace.Close();
                 return usersList;

Initially above code also gets Access Denied Exception in IIS, After changing Application pool fromDefault app pool to  MSExchangePowerShellFrontEndAppPool error resolved.