c# - some powershell commands work from C# ... others won't

Question

I created a powershell script:

mkdir C:\kevin\mySite.com
mkdir C:\kevin\mySite.com\stylesheets
mkdir C:\kevin\mySite.com\slideshows
mkdir C:\kevin\mySite.com\images
mkdir C:\kevin\mySite.com\file
mkdir C:\kevin\mySite.com\js

c:/windows/system32/inetsrv/appcmd add site /name:"mySite.com" /id:187          /physicalPath:C:\kevin\mySite.com

If I run this in powershell it works fine.
I tried running it from a c# web page (code below) the mkdir commands works but the appcmd does not

private string ExecuteScript(string psScript)
{
    string status="";
    try
    {
        Runspace rs = RunspaceFactory.CreateRunspace();
        rs.Open();
        using (rs)
        {
            Pipeline pp = rs.CreatePipeline(psScript);
            pp.InvokeAsync();
        }
        rs.Close();
    }
    catch (InvalidRunspaceStateException ex)
    {
        status = ex.ToString();
    }
    return status;
}

Anyone have any ideas?