Application specfic data in DXF Entities

Question

I'm looking for a way to tag entities (for example arc) in a DXF with an numeric ID of my choosing. Is there a good (standard complient) way of doing this?

Looking at the DXF format reference, I see there is a "common group code" 102 that is documented as "application defined codes". Can I use that? If so an example of the correct way to use it whould be nice.

Answer 1

After asking a similar question on the autodesk forums, I have found that I can use Extended Data to add my numeric ID.

Extended Data is appended at the end of the entity and in my case I will solve it by appending the following:

1001
MYAPP
1002
{
1070
    12
1002
}

• Where 1001 marks the start of extended data
• 1002 marks the beginning end end of list
• 1070 is a 16-bit integer

It's also possible to add extended data from Autocad software using the command _xdata