How to Join FamilyInstance?

[choshQT24J]

My purpose:
I have to difference family file (.rfa).
let's say "a.rfa"(Family A) and "b.rfa"(Family B).

"a.rfa" is void. 

"b.rfa" is solid.

I need to use revit .net api to use Family A to open a hole on Family B.

I have done some researches.
Look like there are two ways for join gemory in revit api.
CombineElement and BooleanOperation.

No matter what I try, I'm having problems.
CombineElement need to use GenericForm. But I don't know how to get GenericForm in FamilyInstance.
BooleanOperation need to use Solid. But I don't know how to get Solid in FamilyInstance.

Could Anyone give me some advice. Thanks.
Sorry for my English.

[WillianMayrink]

Try to use  a class InstanceVoidCutUtils, the method AddInstanceVoidCut()

[satouak]

Thanks  Willian for the reply!!
Same Issue Here. I have tried and got the error "Autodesk.Revit.Exceptions.ArgumentException: 'The element is not a family instance with an unattached void that can cut.
Parameter name: cuttingInstance"

[TripleM-Dev.net]

Hi @choshQT24J ,

First off, can you do it manually in the Revit UI to Cut Family B with Family A.

If that doesn't work then it's also not possible in the API.

The error looks like Family A isn't set to cut, in the family check the option "Cut with voids when loaded".

- Michel

[choshQT24J]

Yes, I have done that manually.
And I have made the family to check with "Cut with voids when loaded".
Maybe I need to provide my family file. I'll prepare for that.

[TripleM-Dev.net · Accepted solution]

Hi @choshQT24J,

Seems a (old) post of @jeremytammik might be the answer: Transaction Group and Regeneration for InstanceVoidCutUtils 

The error message is shown when "Cut with Voids when loaded" isn't checked, but the error is also displayed if the family is placed and Cut without using a Commit between the 2 actions.

So follow this Setup:

1. Start a Transaction Group

2. Start a Transaction

3. Place all Families (including the VoidCut families)

4. Commit and end Transaction of 2.

5. Start a new transaction

6. perform the Cut actions

7. Commit and end transaction of 5.

8. Assimilate (and end) the Transaction Group

- Michel.

[choshQT24J]

Thanks! I'll take a look on it.