risport SelectCmDevice to get phone status

[khoabui76]

anyone know what this error means?

1. RisPort.CmSelectionCriteria rpinfo = new RisPort.CmSelectionCriteria();  

        rpinfo.MaxReturnedDevices = 20;

rpinfo.SelectBy = "9086478757";

        RisPort.SelectCmDeviceResult result =   new RisPort.SelectCmDeviceResult();

RisPort.RisPortTypeClient trythis = new RisPort.RisPortTypeClient();

        RisPort.AstHeader ast = new RisPort.AstHeader();

       ast.SessionId ="SessionId";

        string test = "";

  result= trythis.SelectCmDevice(

ref ast ,

ref test,rpinfo);