You should be using either the RunUnit.Add method and then invoking the class that has been added directly or using the RunUnit.Call method to call a program that has not yet been instantiated or added.
You should not be using both the Add and Call methods togerther.
If you are using ilsmartlinkage then it is recommended that you use the following:
RunUnit runUnit = new RunUnit();
runUnit.Add(xuservg);
int retValue = xuservg.XUSERVG(SExtUebergabeLen, sExtUebergabe, SUservgIoLen, sUservgIo);
This will add the instantiated program to the new RunUnit and then call it using the parameter classes created by ilsmartlinkage.
Thanks.