How to undo Boolean operation in autocad C#

[strsuraj]

My procedure involves union of 2 solids, committing it so that I can get edges of newly formed solid. And then finally selecting required edges to perform fillet.

I am able to do this all perfectly. 

But the problem I face is, if the edges selected doesn't perform fillet due to bigger radius or some other error, it returns back giving me the solid (newly formed after union operation). 

How can I return to the beginning, i.e with 2 different solids ?? 

[_gile]

Hi,

Did you try to perform fillet before committing the Union?

1. Start transaction
2. Union solids
3. Try to Fillet and then then Commit the transaction
4. Catch Abort the transaction

[strsuraj]

Thanks Gile for response.

If I won't commit the union, I won't get to know possible leftover edges after union operation. I may end up picking edges which may possibly won't be part of final solid after the union.