Import module called from C# throws exception

PowerShell powershell = PowerShell.Create();
powerShell.Commands.AddCommand("Import-Module").AddParameter("Name", "virtualmachinemanager");
powerShell.Invoke(); // This throws exception.

InitialSessionState iss = InitialSessionState.CreateDefault();
           iss.ImportPSModule(new string[] { @"C:\vm\vm.psd1"});
           Runspace runSpace = RunspaceFactory.CreateRunspace(iss);
           runSpace.Open();