The "Object reference not set to an instance of an object" error means that the application tried to access a reference type that has not yet been initialized.
The following code example will throw this error:
Dim oPersonnel as CIL.Personnel oPersonnel.FirstName = "Tom"
However, by calling a constructor and creating an instance of the Personnel class, we will be able to assign and then modify a location in memory for the object:
Dim oPersonnel as New CIL.Personnel oPersonnel.FirstName = "Tom"