[Connect] How to save application specific data in a dgn document

Paul Connelly said:

if people want to corrupt their own data

Please explain why Mangesh's example would lead to corrupted data.

Mangesh's example will convert an Item Types schema into something that looks like an Item Types schema but does not behave like one. His exact code will most likely not produce any actual observable problems (but we will not promise that), except that the sneaky read-only flag may be reset upon editing/copying/importing the Item Type Library.

His example casually includes a very dangerous line of code:

Mangesh.Shelar said:

DgnEC.DgnECManager.Manager.UpdateSchema(itLibrary.ECSchema, GetDgnFile(), null);

If someone were to mutilate their Item Type schema in a different way and execute this line of code, existing Items would very likely become unreadable; the Item Types dialog would become confused about the contents of the schema; etc.

Use Item Types if you can accept the constraints imposed by them; otherwise create a custom ECSchema. If you are dissatisfied with those constraints, request an enhancement.

EDIT: I should add that this:

Mangesh.Shelar said:

IECClass cls = itLibrary.ECSchema.GetClass("GeneralSymbols");

IECProperty p = cls["TestProperty"];

p.IsReadOnly = true;

is also a bug. If you want to modify any ECSchema you must make a copy of it, modify the copy, and pass the copy to UpdateSchema().

Thanks Paul for detail explanation.

So summary is, if you try to change underlying schema of ItemType library, whole ItemType feature will behave wrongly.My code snippet was quick test to check if whether ItemType responds to schema changes or not. My test passes, but as Paul suggested it's far risky.

Other option will be: I can file an enhancement for making provision to make ItemType property. Let us see if we can come up with appropriate solution.

Mangesh.Shelar said:

I can file an enhancement for making provision to make ItemType property read-only.

Good idea!

Mangesh.Shelar said:

I can file an enhancement for making provision to make ItemType property read-only.

Good idea!