Navigation

There are basic methods to navigate the primary hierarchy. for example, consider the following hierarchy:

If we are sitting at Zone2, we can navigate as follows:

using NOUN=Aveva.Core.Database.DbElementTypeInstance;

DbElement zone = DbElement.GetElement("/Zone1")

DbElement temp=zone2.Next(); // temp is now Zone3

temp=zone2->Previous(); // temp is now Zone1

temp=zone2->Owner(); // temp is now Site1

temp=zone2->FirstMember(); // temp is now Pipe1

DbElement pipe1=temp;

temp=zone2->LastMember(); // temp is now Equi1

DbElement temp=pipe1.Next(NOUN.EQUIPMENT); // temp is Equi1

DbElement temp=pipe1.Previous(); // temp is ‘null’ as there is no previous element. This can only be tested using the ‘IsNull’ method

Scanning the database is a very common operation. For this reasons there are additional iterator and filter classes that ease this task. These are described in the section on Filters/Iterators.

Pseudo Attributes Relating to Element Navigation

'*'- qualifier is optional

Secondary Hierarchies

Standard navigation methods do not work for descending a secondary hierarchy. Pseudo attribute SMEMB must be used, for example: to get the design elements below a GPSET, you must query the SMEMB attribute on the GPSET.

Pseudo attributes relating to secondary hierarchies are:

The difference between SMEMB and SEXPND is that SEXPND allows for recursive secondary hierarchies. Where there are no recursive possibilities, SMEMB and SEXPND will be the same. The following example illustrates the difference between SMEMB and SEXPND:

In the example there are two secondary nodes S1 and S2. S1 holds element A and C, and S2 holds S1, D and G.

For S1,

SMEMB returns A,C

SEXPND returns A,C

For S2,

SMEMB returns S1,D, G

SEXPND returns A,C, D, G